Centre for Science at Extreme Conditions (CSEC) and School of Chemistry, University of Edinburgh, Mayfield Road, Edinburgh EH9 3JZ (UK).
Angew Chem Int Ed Engl. 2015 Oct 5;54(41):12074-7. doi: 10.1002/anie.201506540. Epub 2015 Aug 26.
Ferrimagnetic A2 BB'O6 double perovskites, such as Sr2 FeMoO6 , are important spin-polarized conductors. Introducing transition metals at the A-sites offers new possibilities to increase magnetization and tune magnetoresistance. Herein we report a ferrimagnetic double perovskite, Mn2 FeReO6 , synthesized at high pressure which has a high Curie temperature of 520 K and magnetizations of up to 5.0 μB which greatly exceed those for other double perovskite ferrimagnets. A novel switching transition is discovered at 75 K where magnetoresistance changes from conventional negative tunneling behavior to large positive values, up to 265 % at 7 T and 20 K. Neutron diffraction shows that the switch is driven by magnetic frustration from antiferromagnetic Mn(2+) spin ordering which cants Fe(3+) and Re(5+) spins and reduces spin-polarization. Ferrimagnetic double perovskites based on A-site Mn(2+) thus offer new opportunities to enhance magnetization and control magnetoresistance in spintronic materials.
亚铁磁 A2BB'O6 双钙钛矿，如 Sr2FeMoO6，是重要的自旋极化导体。在 A 位引入过渡金属为提高磁化强度和调节磁电阻提供了新的可能性。本文报道了一种在高压下合成的亚铁磁双钙钛矿 Mn2FeReO6，其居里温度高达 520K，磁化强度高达 5.0μB，大大超过其他双钙钛矿亚铁磁体。在 75K 时发现了一种新的开关转变，磁电阻从传统的负隧道行为转变为大的正数值，在 7T 和 20K 时高达 265%。中子衍射表明，该开关是由 Mn(2+)自旋的反铁磁有序引起的磁各向异性驱动的，Mn(2+)自旋的反铁磁有序使 Fe(3+)和 Re(5+)自旋倾斜，降低了自旋极化。基于 A 位 Mn(2+)的亚铁磁双钙钛矿为增强自旋电子材料的磁化强度和控制磁电阻提供了新的机会。
