Non-collinear magnetism contra frustration: Magnetic order and anisotropy in hexagonal MnPtGa

TL;DR

This study investigates the complex magnetic behaviors of MnPtGa, revealing that various magnetic states are energetically close, which could be manipulated by external fields to induce different magnetic phenomena.

Contribution

The paper provides first principles calculations showing the near-degeneracy of multiple magnetic orders in MnPtGa, emphasizing the potential for external control of its magnetic state.

Findings

Magnetic energy differences are within 30 meV, comparable to thermal energies at room temperature.

MnPtGa exhibits strongly localized magnetic moments at Mn sites (~3.9 μB).

Multiple magnetic configurations can be stabilized by external fields due to small energy differences.

Abstract

MnPtGa is a hexagonal intermetallic compound with a rich variety of magnetic order. Its magnetic state is reported to range from collinear ferromagnetism, to non-collinear skyrmion type order. MnPtGa is a system with strongly localized magnetic moments at the Mn atoms as was demonstrated using calculations for disordered local moments. The magnetic moments at the Mn sites stay at about 3.9 bohr even above the calculated magnetic transition temperatures (TN = 220 K or TC = 285 K). In the present work, a special emphasis was focused on the possible non-collinear magnetic order using first principles calculations. The investigations included magnetic anisotropy, static noncollinear order in form of spin canting and dynamic non-collinearity in spin spirals. It is found that the energy differences between ferromagnetic, antiferromagnetic, canted, or spiral magnetic order are in the order of not more than 30 meV, which is in the order of thermal energies at ambient temperature. This hints that a particular magnetic state - including skyrmions, antiskyrmions or spin glass transitions - may be forced when an external field is applied at finite temperature.