Theses and Dissertations - Department of Physics & Astronomy
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Browsing Theses and Dissertations - Department of Physics & Astronomy by Subject "Condensed matter physics"
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Item Applications of methods beyond density functional theory to the study of correlated electron systems(University of Alabama Libraries, 2013) Sims, Hunter Robert; Butler, W. H.; University of Alabama TuscaloosaThe difficulty in accurately treating systems in which electron-electron interactions are the dominant physics has plagued condensed matter physics for decades. Currently, there exist many different computational techniques designed to improve upon density functional theory to varying degrees of accuracy. To date, no unified, parameter-free method exists that is guaranteed to yield the correct answer for all materials. Consequently, proper treatment of such systems often requires a combination of several methods, allowing one to check them against one another when their regions of validity overlap and to expand one's reach when a single method cannot reliably describe all of the physics at work. In this dissertation, I present discussion and, when appropriate, brief derivations of several of the most prominent electronic structure methods currently in use---from the local density approximation through LDA+DMFT. I then present several investigations into the electronic and magnetic structure of materials of potential interest for information technology that also illustrate the current state of affairs in computational condensed matter physics. I explore the intersite exchange interactions in CrO_2 within density functional theory (with and without Hubbard “+U” corrections) and evaluate these results through analytic and numerical means. I study the dependence of the mysterious magnetization of Fe_16 N_2 on crystal and electronic structure and employ a wide range of techniques in an attempt to bring greater rigor and deeper understanding to the widely-varying reports on this material. In conjunction with others' careful experimental analysis, I provide a picture of the band structure of the magnetic insulator NiFe_2 O_4 that reveals a novel hierarchy in its band gaps and suggests applications in spintronics and possibly other areas. Finally, I employ dynamical mean-field theory to study the behavior of impurity states in elemental semiconductors, using H impurities in Ge as a base system.Item Dynamic transport measurements of vo2 thin films through the metal-to-insulator transition(University of Alabama Libraries, 2018) Jones, Joshua Michael; LeClair, Patrick R.; University of Alabama TuscaloosaVO2 is a transition metal oxide material well known for its high magnitude metal-to-insulator transition (MIT) with a corresponding change in crystal structure [1]. At room temperature, VO2 is found in an insulating monoclinic phase (P21/c) that upon heating through the transition temperature (Tc, ~341 K in bulk material) changes to a metallic rutile phase (P42/mnm) [2]. The MIT can be activated thermally by heating or cooling through Tc, but has also been shown to be sensitive to electric field [3], infrared radiation [4], pressure [5], and strain [6]. The value of Tc is also highly tunable through doping [7] and growth of strained epitaxial thin films [8]. The massive 3-4 order of magnitude change in electrical resistivity (ρ) has drawn interest for possible device level applications. The transition is characterized by the coexistence of rutile metallic domains and a monoclinic insulating matrix that results in a smooth progression of the DC transport and dielectric properties as the MIT is induced. In this thesis, we present an overview of three novel transport experiments all of which involve epitaxial TiO2/VO2 films grown in a home-built low-pressure chemical vapor deposition system. The first experiment looks at the time evolution of the film resistance and capacitance as it settles for an extended period very near Tc. We report evidence that this settling process is characterized by at least two underlying relaxation processes. The second experiment involves the deposition and ferromagnetic resonance (FMR) characterization of TiO2/VO2/Ru/Py heterostructures. Our analysis indicates enhanced spin pumping into the VO2 layer when in the metallic state that is associated with an increase in the effective Gilbert damping parameter. Finally, we discuss the results of 1/f noise spectroscopy measurements collected on Hall-bar patterned VO2(100) films. We show that the processes governing noise along both crystallographic axes are identical and, in the metallic rutile state, follows a unique R-3 scaling behavior.Item Electron tunneling in the tight-binding approximation(University of Alabama Libraries, 2016) Mackey, Frederick D.; Butler, W. H.; University of Alabama TuscaloosaIn this thesis, we treat tunneling similar to a scattering problem in which an incident wave on a barrier is partially transmitted and partially reflected. The transmission probability will be related to the conductance using a model due to Landauer. Previously tunneling has been treated using a simple barrier model, which assumes the electron dispersion is that of free electrons. In this model it is not possible to investigate tunneling in the gap between a valence band and a conduction band. We shall remedy this limitation by using the tight-binding model to generate a barrier with a gap separating a valence band and a conduction band. To do this, we constructed a model consisting of semi-infinite chains of A atoms on either side of a semi-infinite chain of B-C molecules. The B-C chain has a gap extending between the onsite energy for the B atom and the onsite energy for the C atom. Tunneling through the gap has been calculated and plotted. We present exact closed form solutions for the following tunneling systems: (i) A-B interface, (ii) A-(B-C) interface, (iii) A-B-A tunnel barrier, (iv) A-(B-C) interface with the orbitals on B having s-symmetry and those on C having p-symmetry, (v) A-(B-C)-A tunnel barrier.Item Exploring the magnetic phases in dysprosium by neutron scattering techniques(University of Alabama Libraries, 2014) Yu, Jian; Mankey, Gary J.; University of Alabama TuscaloosaWith one of the highest intrinsic magnetic moments (10.6 μ_B) among the heavy rare-earth elements, dysprosium (Dy) exhibits a rich magnetic phase diagram, including a few modulated magnetic phases. Aided by the Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction, the magnetic modulations propagate coherently over a long range, even with intervening non-magnetic layers. Neutron diffraction experiments were performed to determine the microscopic magnetic origin of the field induced phases in bulk Dy as a function of temperature, covering regions of the well-known ferromagnetic, helical antiferromagnetic, fan phases and several possible new phases suggested by previous studies. A short range ordered (SRO) fan phase was identified as the intermediate state between ferromagnetism and long range ordered (LRO) fan. The temperature range of a coexisting helix/fan phase was also determined. The magnetic phase diagram of Dy was thus refined to include the newly determined magnetic structures and the associated phase boundaries. Based on the period of the magnetic modulation and the average magnetization, the evolution of the spin arrangement upon heating was derived quantitatively for the modulated magnetic phases. To gauge the effect of nanostructuring on the magnetic phases with nonmagnetic Y layers, epitaxial Dy/Y superlattices of various layer thicknesses and repeats were fabricated by magnetron sputtering under carefully controlled conditions. X-ray characterizations confirmed that the crystallographic and interfacial qualities of the superlattices are comparable to those grown by MBE in previous studies. The macroscopic magnetization was characterized by magnetometry, whereas the microscopic magnetic structures were extracted from neutron diffraction and polarized neutron reflectometry (PNR) measurements. The ordering of helical modulation is sensitive to the interfacial roughness of the multilayer as well as the cooling histories. Off-specular PNR was applied the first time to characterize the helical domain structures in Dy/Y multilayers. The lateral correlation length in the helical magnetic structure was in the order of 100 nm.Item Half-metallic CrO_2 thin films for spintronic applications(University of Alabama Libraries, 2011) Pathak, Manjit; LeClair, Patrick R.; University of Alabama TuscaloosaCrO_2 is a well-established half-metallic oxide with near perfect spin polarization - known to have the highest spin polarization among all known materials theoretically as well as experimentally. This means that the conduction electrons in CrO_2 have only one kind of spin i.e. conduction is due only to the majority spin electrons. Because of its high spin polarization, CrO_2 stands as an ideal and one of the most attractive candidates for spin-electronic applications as well as of fundamental interests. The enormous potential of CrO_2 is still untapped since thin film growth modes, interface/surface properties and various factors affecting them are not very well understood or, relatively unknown. Reported works confirm strained growth of (100) CrO_2 films and strain free growth of (110) CrO_2 films on iso-structural TiO_2 substrates investigated using X$ - $ray diffraction. Superconducting quantum interference device (SQUID) and element specific X-ray magnetic circular dichroism (XMCD) techniques were employed to investigate the effect of this substrate-induced strain on the magnetic properties of the films. Magnetic tunnel junctions (MTJ) were fabricated with CrO_2 , Cr_2 O_3 [natural oxide of Cr] as the thin insulating barrier and Co as the other ferromagnetic electrode using photolithography. I-V characteristics of this spin-electronic device are reported. Also, results on the low pressure chemical vapor deposition (CVD) growth of CrO_2 and its comparison with standard growth technique under atmospheric pressure are reported.Item Interfacial interactions of FeCo/Pd and FeCo/Ru multilayers(University of Alabama Libraries, 2009) Walock, Michael James; Mankey, Gary J.; University of Alabama TuscaloosaThe FeCo system of alloys is perched atop the Slater-Pauling curve. As a result of this and its relatively low cost and ease of deposition, it is heavily used within the magnetic recording industry. However, new technology requires an advance past this system with respect to high moment, high magnetization materials. One possible step is the enhancement of the FeCo system. One approach is the lamination of thin, nonmagnetic Pd spacer layers with FeCo. Prior published results have shown an increase in not only the moment, but also the magnetization of the samples. We have developed a FeCo/Pd superlattice samples to test this hypothesis. Our results, using a combination of conventional magnetometry, x-ray magnetic circular dichroism, and polarized neutron reflectivity, show a different result from prior reports. The magnetic dichroism experiments show a definite decrease in the magnetic moments of both the Fe and Co with the introduction of Pd. The preliminary analysis of the neutron reflectivity data shows no increase in the magnetic moment of the alloy, nor an induced moment in the Pd. For comparison with the FeCo/Pd superlattice, we studied an antiferromagnetically coupled FeCo/Ru superlattice.Item Interplay of magnetic anisotropy and magnetization reversal in ferromagnetic thin films for spintronics applications(University of Alabama Libraries, 2016) Paul, Soumalya; Mewes, Tim; University of Alabama TuscaloosaHigh spin-polarization in a magnetic material is essential for excellent performance of future spintronic devices and in that regard, half-metallic materials are promising candidates when incorporated into magnetoresistive devices such as magnetic tunnel junctions (MTJs) for spin transfer torque magnetic random access memory (STT-MRAM). As there is an increasing thrust toward device miniaturization and achieving faster switching times, it is likely that magnetic recording materials will be operating at higher frequencies and hence understanding the interplay between the magnetic anisotropy and the magnetization reversal process is of crucial importance both from technological and fundamental perspectives. Broadband ferromagnetic resonance (FMR) spectroscopy is an excellent tool to probe the dynamic magnetic properties of these half-metallic materials. Our investigation suggests that these low damping materials exhibit ‘anisotropic magnetization relaxation’ due to misfit dislocation (in case of Heusler CoxFe3-xSi thin films) as well as the presence of ‘magnetostatic spin waves’ due to the long-range dipolar interaction (in case of rutile CrO2 thin films). Furthermore, vector magneto-optic Kerr effect (MOKE) magnetometry reveals that single crystal CrO2 thin films are magneto-optically anisotropic with two different refractive indices. The structural anisotropy of the tetragonal CrO2 induces the magneto-optical anisotropy. On the other hand, changing the stoichiometry in epitaxial CoxFe3-xSi thin films results in the co-existence of the uniaxial magnetic anisotropy and the cubic magnetic anisotropy. The magnetization reversal processes are associated with the one-jump and two-jump reversal steps that depend critically on the competition between the uniaxial and cubic anisotropies present in these samples.Item Magnetic anisotropies and dynamic magnetic properties in multilayered thin films(University of Alabama Libraries, 2017) Beik Mohammadi, Jamileh; Mewes, Tim; Mewes, Claudia K. A.; University of Alabama TuscaloosaTheoretical and experimental research on magnetic materials and magnetic devices intend to investigate novel materials and structures which can be used for the next generation spintronic devices. Moreover, it is essential to conduct fundamental research on new phenomena aiming for new generation of devices that can be faster, smaller, cheaper, and more reliable. Magnetic anisotropies have been widely used in spintronic devices. From the unidirectional exchange bias anisotropy that is used in magnetic read heads and giant magnetic resonance (GMR) sensors, to the interfacial perpendicular magnetic anisotropy (PMA) that is essential for magnetic tunnel junctions (MTJs). In the first chapter of this dissertation a short introduction to magnetization dynamics including experimental techniques is given. In the second chapter, the exchange bias anisotropy and the interfacial origin of relaxation in Ru/IrMn/CoFe/Ru exchange biased systems is discussed and investigated. The interfacial perpendicular anisotropy is observed in these systems and can be quantified using FMR technique. Such anisotropy can exist in a thin ferromagnetic film (such as NiFe) that is in proximity to a metallic (e.g.Ru) or insulating (e.g. SiO2) non-magnetic layer, which is the topic of the third chapter of this dissertation. In addition, experimental results confirm that spatial fluctuations of the uniaxial perpendicular anisotropy can push the easy axis of the magnetization in an orientation that is neither perpendicular to the film nor normal to it. The effect of the lateral fluctuation of the uniaxial anisotropy on the magnetic energy landscape and the magnetization dynamics of thin magnetic layers is reported in chapter four using micromagnetic simulations.Item Magnetic anisotropy graded media and Fe-Pt alloy thin films(University of Alabama Libraries, 2009) Lu, Zhihong; Butler, W. H.; University of Alabama TuscaloosaAnisotropy graded media is promising to overcome the writability problem in achieving ultrahigh areal density for magnetic recording media. To more conveniently study and compare various media with regard to a particular figure of merit, a new energy landscape method of analysis is suggested. Using this method, the theoretical limit of the figure of merit for a graded medium is found to be 4. This limit can be approached by a graded medium with anisotropy quadratically increasing from zero to its maximum value. In order to characterize the anisotropy distribution of a graded medium, hard axis loops of graded media with various anisotropy profiles are simulated and analyzed. It is found that the second derivative of the hard axis loop can give useful information on the anisotropy distribution in a graded medium. Fe₅₀Pt₅₀ with the L1₀ structure, as one of the magnetically hardest materials, has great potential for media application. By using a first-principles calculation method, the magnetic and electronic structures of L1₀ structured Fe₅₀Pt₅₀ have been studied. These calculations show that although the ferromagnetic phase is the most stable phase for Fe₅₀Pt₅₀ with the L1₀ structure, there is a competition between the antiferromagnetic and the ferromagnetic phases when the ratio of lattice constants, c/a, decreases. Experimental investigations of Fe₅₀Pt₅₀ films with graded order parameter fabricated by varying the growth temperature during deposition demonstrate that these films have much smaller switching field than fully ordered Fe₅₀Pt₅₀, which suggests it is possible to make graded media by using this kind of films. Fe₁₀₋ₓPtₓ films with compositional gradient were also studied; however, the large easy axis dispersion in these films makes them unsuitable for the fabrication of graded media. Films with [FePt₃ordered)/FePt₃ (disordered)]n superlattices were deposited on MgO substrates and sapphire substrates. It was found that the exchange bias in superlattices deposited on MgO substrate show higher exchange bias field. Polarized neutron reflectivity results show that ferromagnetic layers on MgO substrates contain more antiferromagnetic component than those on sapphire substrates. The larger exchange bias of the superlattice on MgO substrate is hypothesized to be due to larger exchange bias in its ferromagnetic layers.Item Novel antimony-based Heuslers with potential spintronic applications(University of Alabama Libraries, 2017) Naghibolashrafi, Nariman; Gupta, Arunava; University of Alabama TuscaloosaThe Heusler alloys, or compounds to be precise, have become a well-known name among materials scientists, solid-state physicists and other researchers of the field. In this set of studies, we examined a ternary system, i.e. Fe-Ti-Sb using experimental methodology comprised of different microstructural and structural tests alongside theoretical evaluations. The results showed that there was a compound present in the system, Fe1.5TiSb, which had the structural hall marks of a Heusler, albeit with vacancies in the tetragonal positions. This meant that the compound not only was most probably ‘layered’ between half a full Heusler, but also it was paramagnetic, the compound exhibited a novel Slater-Pauling behavior. The next system studied was FexCo1-xTiSb, eventually leading to observation of a novel half Heusler compound, Fe0.5Co0.5TiSb. The compound showed a C1b signature and no sign of any other phase were witnessed microstructurally. Magnetometry and transport measurements revealed the nature of the material to be an antiferromagnetic material with possible semiconductivity. Theoretical evaluations further validated the possibility of an antiferromagnetic coupling between iron and cobalt in this compound. Following the discovery of the Fe1.5TiSb, colleagues in our theory group encouraged us to look into another possible ‘layered’ Heusler, Co1.5TiSn, based on the former compound’s prototype. The experiments not only found that the Co1.5TiSn has all the hallmarks of a Heusler, but also magnetometry tests, especially the interesting evaluation of a Rhodes-Wohlfarth model, led to conclusion that the compound has half-metallic characteristics. The bandstructure calculated through first-principles methods also initially predicated this half metallic nature.Item Pair hopping in the short-range RVB model: observable implications for cuprate superconductors(University of Alabama Libraries, 2015) Lovorn, Timothy Foster; Sarker, Sanjoy Kumar; University of Alabama TuscaloosaThe development of a microscopic model which successfully describes cuprate superconductors, particularly underdoped ones, has remained an elusive goal. The t-J model has been widely used as a starting point for the development of such a model; it describes a single band of electrons hopping on a lattice and experiencing an exchange interaction, subject to the constraint that at most one electron can occupy any site. In some circumstances the t-J model exhibits spin-charge separation, in which electrons remain localized but particles carrying only charge (holons) and only spin (spinons) delocalize separately. In this dissertation, we study a recently-developed model Hamiltonian which is derived from the t-J model by renormalization of high-energy holon hopping processes which break spin singlets. This renormalization introduces a holon pair hopping term which provides a basis for the development of superconductivity. The renormalized model is constrained by continuity with the well-understood behavior of the t-J model at half-filling (when there is exactly one electron per site); it matches the symmetry of the known spin states. Here we analyze the renormalized model by mean-field theory and by studying pair fluctuations self-consistently. We reproduce the basic features of the cuprate phase diagram at low hole doping, including the d_x^2 _-y^2 symmetry of the superconducting gap and the two-dimensionality of the pseudogap phase. Importantly, we find a separation of temperature scales between the formation of charged pairs and their condensation. We qualitatively reproduce experimental signatures of paring at temperatures above the superconducting transition by studying the specific heat and diamagnetic response.Item Raman spectroscopy of double- and triple-walled carbon nanotubes: fundamental, combination, and overtone modes(University of Alabama Libraries, 2020) Hue, Jia Wern; Araujo, Paulo T.; University of Alabama TuscaloosaA single-walled carbon nanotube (SWNT) is a graphene sheet rolled up into a tube. Double-walled (DWNT) and triple-walled carbon nanotubes (TWNT) are two and three coaxial SWNTs respectively. Isolated species of DWNTs and TWNTs were only recently probed and it can be considered as a new branch in carbon nanotube science. Phonons, and the combination of phonons and overtones are fundamental to understanding optical processes, transport and thermoelectricity in carbon nanotubes. To study these phonons, resonance Raman spectroscopy is employed on DWNT and TWNT bundles, as well as isolated TWNTs. The phonon modes of interest to this dissertation are the radial breathing mode (RBM), the G-band, and the M-band. From the RBM, it is learnt that for inner tubes with a tube diameter less than 1.2 nm, the curvature effects are dominant. Evidence for intertube interactions was found, although for outer tubes the environmental effects dominate. There was also evidence for commensurate and incommensurate tubes. Studying the G-band allowed for possible chiral indices to be identified for the middle and outer tubes of isolated TWNTs. In addition, the frequency shifts of TWNT G-band frequencies relative to SWNT G-band frequencies were studied and compared to TWNT G-band frequency shifts. As for the M-bands, phonon mode assignments for peaks between 1680 cm-1 to 1850 cm-1 were attempted.Item Search for effective spin injection heterostructures based on half-metal heusler alloys/gallium arsenide semiconductors: a theoretical investigation(University of Alabama Libraries, 2016) Sivakumar, Chockalingam Sivakumar; Butler, W. H.; University of Alabama TuscaloosaEfficient electrical spin injection from half-metal (HM) electrodes into semiconducting (SC) channel material is a desirable aspect in spintronics, but a challenging one. Half-metals based on the Heusler alloy family are promising candidates as spin sources due to their compatibility with compound SCs, and very high Curie temperatures. Numerous efforts were made in the past two decades to grow atomically abrupt interfaces between HM_Heusler and SC heterostructures. However, diffusion of magnetic impurities into the semiconductor, defects and disorder near the interface, and formation of reacted phases were great challenges. A number of theoretical efforts were undertaken to understand the role of such material defects in destroying the half-metallicity and also to propose promising half-metal/SC heterostructures based on first principles. This dissertation summarizes the investigations undertaken to decode the complexity of, and to understand the various physical properties of, a number of real-world Heusler/SC heterostructure samples, based on the ab initio density functional theory (DFT) approach. In addition, it summarizes various results from the first principles-based search for promising half-metal/SC heterostructures. First, I present results from DFT-based predictive models of actual Co_2MnSi (CMS)/GaAs heterostructures grown in (001) texture. I investigate the physical, chemical, electronic, and magnetic properties to understand the complexity of these structures and to pinpoint the origin of interfacial effects, when present. Based on the investigations of such models, I discuss the utility of those actual samples in spintronic applications. Next, I summarise the results from an ab initio DFT-based survey of 6 half-Heusler half-metal/GaAs heterostructure models in (110) texture, since compound semiconductors such as GaAs have very long spin lifetime in (110) layering. I show 3 half-Heusler alloys (CoVAs, NiMnAs, and RhFeGe), that when interfaced with GaAs(110), fully preserve the half-metallicity at the interface. Finally, I show the advantages of inserting half-Heusler SCs, particularly CoTiAs and CoTiSb, as spacers in between CMS/GaAs systems in (110) layering. Based on DFT calculations, I show that CoTiAs is a promising spacer that could enhance the perpendicular magnetic anisotropy in CMS, while preserving the important half-metallic character at the heterojunctions between CMS/CoTiAs/GaAs(110). This spacer could also serve to prevent in-diffusion of magnetic impurities into the channel material.Item Study of structural and magnetic properties of intermetallic thin films(University of Alabama Libraries, 2016) Manoharan, ezhil arasan; Mankey, Gary J.; University of Alabama TuscaloosaIntermetallic thin films have tunable magnetic properties. The magnetic phases of intermetallic thin films were tuned by changing the alloy composition of the intermetallic system. L10 Fe50Pt50 thin film has high magnetic anisotropy which makes them ideal candidates for the thin film recording media. Magnetic phases of Fe50Pt50 can be tuned by the addition of third element like Mn by forming Fe50-x Mnx Pt50 ternary alloy system. In this work magnetic phases of ordered Fe rich Fe50-xMnxPt50 and Mn rich Fe50-xMnxPt50 thin films of Fe50-x Mnx Pt50 alloy system is investigated. Fe rich Fe50-xMnxPt50 thin films are epitaxially grown on a- Al2O3 and MgO (100) substrates, while Mn rich Fe50-xMnxPt50 thin films are grown on MgO (100) substrates. The change in the magnetic properties in Fe rich Fe50-xMnxPt50 thin films due to presence of tetragonal phase and the prediction of a the presence of a new low temperature phase in the Mn rich Fe50-xMnxPt50 thin films is verified. These intermetallic films are produced in a Ultra High Vacuum sputtering system with Reflective High Energy Electron Diffraction and Auger electron spectroscopy. RHEED is used to verify epitaxy and Auger electron spectroscopy measures chemical composition.Item Synthesis and characterization of novel electronic and magnetic systems(University of Alabama Libraries, 2016) Keshavarz, Sahar; LeClair, Patrick R.; University of Alabama TuscaloosaFabrication and characterization of novel electronic and magnetic materials are pursued under two main subjects during this dissertation: Part I deals with the low frequency noise spectroscopy of vanadium dioxide (VO2) thin films in the vicinity of the first-order metal-insulator transition (MIT). High quality epitaxial thin films of vanadium dioxide were deposited on TiO2 substrates using chemical vapor deposition methods and characterized for our investigations. The design and characterization of our home-built “cross-spectrum” analyzer, which was used for the fluctuation spectroscopy of VO2 films, is explained. 1/f noise analysis of vanadium dioxide across the MIT shows the significant increase of noise amplitude, which can be explained by “Local interference” model. Energy distribution investigations in this material showed the signature of the percolation model. Critical exponent studies are suggestive of the p-noise model as the mechanisms governing the electronic processes in VO2. Evidence of anisotropic electrical transport along different crystallographic axes of VO2 is presented by the conductance, Hall measurements and noise spectroscopy of the patterned VO2 films. Part II of this dissertation presents the systematic, theoretical, experimental and analytical search for novel half-metallic Heusler compounds. Experimental and analytical methods to synthesize and characterize these new materials in polycrystalline bulk form are thoroughly discussed. As a result of our investigation a new Heusler material with the composition of Fe1.5TiSb was synthesized and was recognized as the most stable compound in FexTiSb systems. The theoretical investigations of this system are suggestive of an alternative L21/C1b layered structure for this new phase of material with weak magnetism and metallic characteristics. Our investigations for finding half-metallic Heusler Fe2MnGe led to synthesizing this compound with the hexagonal DO19 structure. This material has a high magnetic moment and uniaxial crystalline anisotropy, which is a step toward finding the half-metallic hexagonal Heusler compounds with applications in perpendicular media and CPP-GMR.