Probing the Néel Order in Altermagnetic RuO<sub>2</sub> Films via X-Ray Magnetic Linear Dichroism
Yichi Zhang, Hua Bai, Dong-Hui 东辉 Zhang 张, Chong 崇 Chen 陈, Lei 磊 Han 韩, Shi-Xuan 诗萱 Liang 梁, Rui-Yue 瑞月 Chu 褚, Jian-Kun 健坤 Dai 戴, Maciek Sawicki, Feng 峰 Pan 潘, Cheng 成 Song 宋
Abstract
Abstract The emerging altermagnetic RuO 2 with both compensated magnetic moments and broken time-reversal symmetry possesses nontrivial magneto-electronic responses and nonrelativistic spin currents that are closely related to the magnetic easy axis. Ru M 3 -edge X-ray magnetic linear dichroism (XMLD) measurements were performed to probe the Néel order in RuO 2 . For epitaxial RuO 2 films, characteristic XMLD signals were observed for either RuO 2 (100) or RuO 2 (110) at normal incidence or RuO 2 (001) at oblique incidence. The signals disappeared when the test temperature exceeded the Néel temperature. For non-epitaxial RuO 2 films, the flat lines in the XMLD patterns of RuO 2 (100) and RuO 2 (110) demonstrate that there is no in-plane uniaxial alignment of the Néel order in these samples because of the counterbalanced Néel order of the twin crystals, as evidenced by X-ray diffraction phi-scan measurements. Our experimental results unambiguously demonstrate antiferromagnetism in RuO 2 films and reveal the spatial relation of the Néel order parallel to the RuO 2 [001] crystalline axis. These findings deepen the understanding of RuO 2 and other attractive altermagnetic materials used in the field of spintronics.