Spin Model for Nontrivial Magnetic Orders in the Inverse-Perovskite Antiferromagnets

TL;DR

This paper develops a classical spin model to explain complex magnetic orders in inverse-perovskite manganese nitrides, successfully reproducing experimental patterns and elucidating the underlying physics of their magnetism and negative thermal expansion.

Contribution

It introduces a novel spin model that captures the magnetic anisotropy and frustration in inverse-perovskite manganese nitrides, solving a long-standing problem in understanding their magnetic behavior.

Findings

Reproduces experimentally observed triangular spin patterns

Analyzes the evolution of magnetic orders systematically

Provides insights into magnetism-driven negative thermal expansion

Abstract

Nontrivial magnetic orders in the inverse-perovskite manganese nitrides are theoretically studied by constructing a classical spin model describing the magnetic anisotropy and frustrated exchange interactions inherent in specific crystal and electronic structures of these materials. With a replica-exchange Monte-Carlo technique, a theoretical analysis of this model reproduces the experimentally observed triangular \Gamma^{5g} and \Gamma^{4g} spin ordered patterns and the systematic evolution of magnetic orders. Our work solves a 40-year-old problem of nontrivial magnetism for the inverse-perovskite manganese nitrides and provides a firm basis for clarifying the magnetism-driven negative thermal expansion phenomenon discovered in this class of materials.