Magnetic anisotropy energy of antiferromagnetic L1-type equiatomic Mn alloys

Abstract

The theoretical calculations of magnetic anisotropy energy (MAE) for antiferromagnetic L10-type MnTM [transition metal (TM)=Ni, Pd, Pt, Rh, and Ir] alloys were carried out on the basis of the local spin-density approximation using linear muffin-tin orbital method with atomic sphere approximation including the spin-orbit interaction. It has been demonstrated that the magnitude of the MAE for L10-type MnIr alloy is highest, −20.77×106J∕m3, and the negative sign of the MAE is consistent with the reported spin structure. On the other hand, the sign of the MAE for L10-type MnPt alloy is positive in accordance with the spin structure. The MAE of the MnPt alloy is sensitive to the electron number, which would be correlated with the fact that only the MnPt alloy system exhibits a complicated magnetic phase diagram.

Magnetic properties of Fe-doped MnAl

“…Furthermore, Mn is a relatively inexpensive metal, which is of utmost importance in light of the current tight supply and high cost of the rare-earth elements that are used in current advanced magnets [1]. Unfortunately, most manganese compounds are antiferromagnetic, which is typical for compounds formed from elements in the middle of the 3d series [2,3]. This situation precludes the use of Mn in many applications that require ferromagnetic materials.…”

“…For example, MnPt alloys with the tetragonal L1 0 structure are antiferromagnetic with high Néel temperatures resulting from antiparallel coupling between adjacent Mn atom located in (001)-planes [4]. Similarly, MnRh, MnPd, MnIr and MnNi alloys are also antiferromagnetic [2]. It is important to understand how the magnetic properties of Mn-based compounds depend upon chemical and structural details.…”

Atomistic spin model based on a spin-cluster expansion technique: Application to the IrMn3/Co interface

“…Regarding the anisotropy, Umetsu et al 8 calculated the magnetic anisotropy energy (MAE) of L1 0 -type MnTM (TM=Ni, Pd, Pt, Rh and Ir) compounds and revealed that MnIr had the highest MAE with a value of -7.05 meV/unit cell. Furthermore, a giant second order magnetic anisotropy for L1 2 IrMn 3 was reported, leading to energy barriers of the order of K eff = 10.4 meV/unit cell for rotation of the T 1 ground state spin-structure around the (111) axis.…”

Graded permanent magnets

“…An example of an antiferromagnet with very strong easy-plane anisotropy is MnIr ͑K 1 = −21 MJ/ m 3 ͒. 17 An experimental approach would be to start from an easyplane magnet and to use mechanical alloying ͑ball milling͒ to create oblique nanoscale interfaces. For example, Sm 2 Co 14 B, which has a room-temperature magnetization of 1.51 T and an anisotropy of −12.0 MJ/ m 3 , 18 compared to +4.9 T for Nd 2 Fe 14 B, would then yield a fairly hard material.…”