Large magnetocrystalline anisotropy in tetragonally distorted Heuslers: a systematic study

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.

8 pages, 5 figures

References in corpus (3)

• Guidelines for understanding cubic manganese-rich Heusler compounds
• Martensitic transition, ferrimagnetism and Fermi surface nesting in Mn_2NiGa
• First-principles study of the lattice instabilities in Mn${}_2$Ni{\it X} ({\it X}= Al, Ga, In, Sn) magnetic shape memory alloys

Cited by in corpus (6)

• Correlation effects on ground-state properties of ternary Heusler alloys: first-principles study
• Exploration of all-3d Heusler alloys for permanent magnets: an ab initio based high-throughput study
• Phase stability and the effect of lattice distortions on electronic properties and half-metallic ferromagnetism of Co2FeAl Heusler alloy: An ab initio study
• Effect of Point Defects and Lattice Distortions on the Structural, Electronic, and Magnetic properties of Co${}_2$MnAl Heusler alloy
• Stability and magnetic properties of grain boundaries in the inverse Heusler phase Fe${}_2$CoGa and in bcc Fe
• Magnetic phase diagram of the austenitic Mn-rich Ni-Mn-(In,Sn) Heusler alloys