Structure, site-specific magnetism and magneto-tra

Structure, site-specific magnetism and magneto-transport properties of epitaxial D0

22
Mn

2
Fe

x
Ga thin films
Davide Betto, Yong-Chang Lau, Kiril Borisov, Kurt Kummer, N.B. Brookes, Plamen Stamenov, J.M.D. Coey, Karsten Rode
(Submitted on 5 Apr 2017)
Ferrimagnetic Mn

2
Fe

x
Ga
(0.26≤x≤1.12)
thin films have been characterised by X-ray diffraction, SQUID magnetometry, X-ray absorption spectroscopy, X-ray magnetic circular dichroism and M\"{o}ssbauer spectroscopy with the aim of determining the structure and site-specific magnetism of this tetragonal , D0

22
-structure Heusler compound. High-quality epitaxial films with low RMS surface roughness (
∼0.6
nm) are grown by magnetron co-sputtering. The tetragonal distortion induces strong perpendicular magnetic anisotropy along the
c
-axis with a typical coercive field
μ
0
H∼0.8
T and an anisotropy field ranging from
6
to
8
T. Upon increasing the Fe content
x
, substantial uniaxial anisotropy,
K
u
≥1.0
MJ/m

3
can be maintained over the full
x
range, while the magnetisation of the compound is reduced from
400
to
280
kA/m. The total magnetisation is almost entirely given by the sum of the spin moments originating from the ferrimagnetic Mn and Fe sublattices, with the latter being coupled ferromagnetically to one of the former. The orbital magnetic moments are practically quenched, and have negligible contributions to the magnetisation. The films with
x=0.73
exhibit a high anomalous Hall angle of
2.5
% and a high Fermi-level spin polarisation, above
51
%, as measured by point contact Andreev reflection. The Fe-substituted Mn

2
Ga films are highly tunable with a unique combination of high anisotropy, low magnetisation, appreciable spin polarisation and low surface roughness, making them very strong candidates for thermally-stable spin-transfer-torque switching nanomagnets with lateral dimensions down to
10
nm.

https://arxiv.org/abs/1704.01326