## Magnetic properties and structure of low temperature phase MnBi with island structure

##### Date

##### Journal Title

##### Journal ISSN

##### Volume Title

##### Publisher

##### Abstract

The magnetic properties of the lowtemperature phase (LTP) MnBi thin films of islands structure are discussed. The LTP MnBi islands are formed onto silica substrates after the multilayers {Bi(3.2nm)/Mn(2nm)}x N are deposited and then annealed at 450C for 0.5hr, where N is the number of the repetition of a pair of Mn and Bi layer. Those islands are found to be of the LTP MnBi, with the c-axis orientation along the normal to the sample plane for N= 10 similar to 40. Their size vary from place to place, but are averagely of about a few hundred nm in height and a few mu m in width for N from 10 to 40. For N= 200, the elongated islands are formed densely, with the length of about a few tens of mu m. The coverage of those islands increases with N. The temperature dependence of saturation magnetization Ms is qualitatively similar to that for bulk, though the absolute values for Ms are smaller by 20%. The magnetic anisotropy constants of K-u1 and K-u2 are evaluated for the samples with N= 10 similar to 40, where K-u1 and K-u2 are the magnetic anisotropy constants corresponding to the second and fourth power term in the uniaxial magnetic anisotropy energy expression. It is found that the K-u1 increases with T monotonously, reaching to about 1x10(7) erg/cc at 400K. On the other hand, the K-u2 remains nearly zero for temperatures below 300K, and then becomes negative, reaching to about 7 x 10(6) erg/cc at 400K. This is the first to report of the temperature dependence of K-u1 and K-u2 in the LTP MnBi of an island structure. It is also noted that the decrease of K-u for a temperature range beyond around 450 K is possibly due to the decrease of the K-u2 component, as demonstrated in the present study. (C) 2017 Author(s).