Wang Zhi-Cheng, Rogers Jared D, Yao Xiaohan, Nichols Renee, Atay Kemal, Xu Bochao, Franklin Jacob, Sochnikov Ilya, Ryan Philip J, Haskel Daniel, Tafti Fazel
Departments of Physics, Boston College, 140 Commonwealth Avenue, Chestnut Hill, MA, 02467, USA.
Physics Department, University of Connecticut, Storrs, CT, 06269, USA.
Adv Mater. 2021 Mar;33(10):e2005755. doi: 10.1002/adma.202005755. Epub 2021 Jan 29.
Materials with strong magnetoresistive responses are the backbone of spintronic technology, magnetic sensors, and hard drives. Among them, manganese oxides with a mixed valence and a cubic perovskite structure stand out due to their colossal magnetoresistance (CMR). A double exchange interaction underlies the CMR in manganates, whereby charge transport is enhanced when the spins on neighboring Mn and Mn ions are parallel. Prior efforts to find different materials or mechanisms for CMR resulted in a much smaller effect. Here an enormous CMR at low temperatures in EuCd P without manganese, oxygen, mixed valence, or cubic perovskite structure is shown. EuCd P has a layered trigonal lattice and exhibits antiferromagnetic ordering at 11 K. The magnitude of CMR (10 %) in as-grown crystals of EuCd P rivals the magnitude in optimized thin films of manganates. The magnetization, transport, and synchrotron X-ray data suggest that strong magnetic fluctuations are responsible for this phenomenon. The realization of CMR at low temperatures without heterovalency leads to a new regime for materials and technologies related to antiferromagnetic spintronics.
具有强磁阻响应的材料是自旋电子技术、磁传感器和硬盘的核心。其中，具有混合价态和立方钙钛矿结构的锰氧化物因其巨大的磁阻（CMR）而脱颖而出。双交换相互作用是锰氧化物中CMR的基础，当相邻的Mn和Mn离子上的自旋平行时，电荷传输会增强。此前寻找不同材料或CMR机制的努力导致的效应要小得多。本文展示了在不含锰、氧、混合价态或立方钙钛矿结构的EuCdP中，低温下出现了巨大的CMR。EuCdP具有层状三角晶格，在11K时表现出反铁磁有序。EuCdP生长态晶体中的CMR大小（10%）与优化后的锰氧化物薄膜相当。磁化、输运和同步加速器X射线数据表明，强磁涨落是这一现象的原因。在没有异价性的情况下实现低温CMR，为与反铁磁自旋电子学相关的材料和技术带来了新的领域。
