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arXiv · 1702.08150

Large magnetocrystalline anisotropy in tetragonally distorted Heuslers: a systematic study

Y. -i. Matsushita·G. Madjarova·J. K. Dewhurst·S. Shallcross·C. Felser·S. Sharma·E. K. U. Gross
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Abstract

With a view to the design of hard magnets without rare earths we explore the possibility of large magnetocrystalline anisotropy energies in Heusler compounds that are unstable with respect to a tetragonal distortion. We consider the Heusler compounds Fe$_2$YZ with Y = (Ni, Co, Pt), and Co$_2$YZ with Y = (Ni, Fe, Pt) where, in both cases, Z = (Al, Ga, Ge, In, Sn). We find that for the Co$_2$NiZ, Co$_2$PtZ, and Fe$_2$PtZ families the cubic phase is always, at $T=0$, unstable with respect to a tetragonal distortion, while, in contrast, for the Fe$_2$NiZ and Fe$_2$CoZ families this is the case for only 2 compounds -- Fe$_2$CoGe and Fe$_2$CoSn. For all compounds in which a tetragonal distortion occurs we calculate the MAE finding remarkably large values for the Pt containing Heuslers, but also large values for a number of the other compounds (e.g. Co$_2$NiGa has an MAE of -2.11~MJ/m$^3$). The tendency to a tetragonal distortion we find to be strongly correlated with a high density of states at the Fermi level in the cubic phase. As a corollary to this fact we observe that upon doping compounds for which the cubic structure is stable such that the Fermi level enters a region of high DOS, a tetragonal distortion is induced and a correspondingly large value of the MAE is then observed.

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Y. -i. Matsushita, G. Madjarova, J. K. Dewhurst, S. Shallcross, C. Felser, S. Sharma, E. K. U. Gross. 2017-02-27. Large magnetocrystalline anisotropy in tetragonally distorted Heuslers: a systematic study. https://doi.org/10.1088/1361-6463/aa5441

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