Manna Rudra Sekhar, Das Pintu, de Souza Mariano, Schnelle Frank, Lang Michael, Müller Jens, von Molnár Stephan, Fisk Zachary
Institute of Physics, Goethe-University Frankfurt, 60438 Frankfurt (Main), SFB/TR49, Germany.
Department of Physics, Florida State University, Tallahassee, Florida 32306, USA.
Phys Rev Lett. 2014 Aug 8;113(6):067202. doi: 10.1103/PhysRevLett.113.067202. Epub 2014 Aug 5.
The coupling of magnetic and electronic degrees of freedom to the crystal lattice in the ferromagnetic semimetal EuB(6), which exhibits a complex ferromagnetic order and a colossal magnetoresistance effect, is studied by high-resolution thermal expansion and magnetostriction experiments. EuB(6) may be viewed as a model system, where pure magnetism-tuned transport and the response of the crystal lattice can be studied in a comparatively simple environment, i.e., not influenced by strong crystal-electric field effects and Jahn-Teller distortions. We find a very large lattice response, quantified by (i) the magnetic Grüneisen parameter, (ii) the spontaneous strain when entering the ferromagnetic region, and (iii) the magnetostriction in the paramagnetic temperature regime. Our analysis reveals that a significant part of the lattice effects originates in the magnetically driven delocalization of charge carriers, consistent with the scenario of percolating magnetic polarons. A strong effect of the formation and dynamics of local magnetic clusters on the lattice parameters is suggested to be a general feature of colossal magnetoresistance materials.
通过高分辨率热膨胀和磁致伸缩实验，研究了铁磁半金属EuB(6)中磁自由度和电子自由度与晶格的耦合，该材料呈现出复杂的铁磁序和巨大磁阻效应。EuB(6)可被视为一个模型系统，在这个相对简单的环境中（即不受强晶体电场效应和 Jahn-Teller 畸变影响），可以研究纯磁调谐输运和晶格响应。我们发现了非常大的晶格响应，其通过以下方式量化：(i) 磁格林艾森参数；(ii) 进入铁磁区域时的自发应变；(iii) 顺磁温度范围内的磁致伸缩。我们的分析表明，晶格效应的很大一部分源于载流子的磁驱动离域，这与渗透磁极化子的情况一致。局部磁团簇的形成和动力学对晶格参数的强烈影响被认为是巨大磁阻材料的一个普遍特征。
