반강자성 (AFM) 재료는 스핀트로닉스 응용 및 새로운 위상현상으로 인해 많은 관심을 받아왔다. 그러나 AFM 재료의 스핀구성을 감지하고 식별하는 것은 순 자화가 없기 때문에 매우 어렵다.  본 연구팀은 평면 홀 효과 (planar Hall effect) 를 활용하여 “클러스터 자기 다중극”을 반강자성 Nd2Ir2O7 박막에서 감지하고 구별하였다. Nd2Ir2O7의 스핀 구조에 압축 변형을 가함으로써 인공적으로 클러스터 자기 다중극자, 즉 dipole, A2 와 T1 octupole 극자를 유도했다. 중요한 것은 자기장 회전 하에서 각 자기 다중극은 PHE 진동의 독특한 고조파를 나타낸다. 더불어, 평면 홀 전도도는 비선형 자기장 의존성을 가지며, 이는 클러스터 octupole의 자기 응답에 기인할수있다. 우리의 작업은 AFM 시스템에서 클러스터 자기 다중극을 식별하기 위한 전략을 제공하고 octupole 기반 AFM 스핀트로닉스를 촉진할 것으로 기대해 볼 수있다.

Antiferromagnetic (AFM) materials are attracting tremendous attention due to their spintronic applications and associated novel topological phenomena. However, detecting and identifying the spin configurations in AFM materials are quite challenging due to the absence of net magnetization. Herein, we report the practicality of utilizing the planar Hall effect (PHE) to detect and distinguish “cluster magnetic multipoles” in AFM Nd₂Ir₂O₇ (NIO-227) fully strained films. By imposing compressive strain on the spin structure of NIO-227, we artificially induced cluster magnetic multipoles, namely dipoles and A₂- and T₁-octupoles. Importantly, under magnetic field rotation, each magnetic multipole exhibits distinctive harmonics of the PHE oscillation. Moreover, the planar Hall conductivity has a nonlinear magnetic field dependence, which can be attributed to the magnetic response of the cluster magnetic octupoles. Our work provides a strategy for identifying cluster magnetic multipoles in AFM systems and would promote octupole-based AFM spintronics.

Authors: Jeongkeun Song, Taekoo Oh, Eun Kyo Ko, Ji Hye Lee, Woo Jin Kim, Yangyu Zhu, Bohm-Jung Yang, Yangyang Li * & Tae Won Noh* (* co-corresponding authors).

Nature Communications 13, 6501 (2022)

DOI: https://doi.org/10.1038/s41467-022-34189-6

Published online: 30 October 2022

Link: https://www.nature.com/articles/s41467-022-34189-6