Regensburg 2016 – scientific programme
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MA: Fachverband Magnetismus
MA 17: Poster Session I
MA 17.57: Poster
Tuesday, March 8, 2016, 09:30–12:30, Poster B1
Charge-spin-lattice correlations in the half-metallic CMR material HgCr2Se4 — •S. Hartmann1, E. Gati1, C. Lin2, Y. Shi2, Y. Li2, J. Müller1, and M. Lang1 — 1Physikalisches Institut, Goethe Universität, SFB/TR49, 60438 Frankfurt, Germany — 2Institute of Physics, Chinese Academy of Sciences, Beijing, China
Understanding the origin of large or colossal magnetoresistance (CMR) effects, observed in a wide range of materials, including hexaborides, remains a challenging field of research in magnetism. The universal occurrence of electronic and magnetic phase separation in these materials has led researchers to suggest the intriguingly simple model of percolating magnetic polarons as a possible mechanism to explain the CMR. In a recent study on the ferromagnetic semimetal EuB6, where the existence of percolating nano-scale magnetic clusters is established, we found a very large lattice response at the ferromagnetic transition, a significant part of which originates in the magnetically-driven delocalization of charge carriers [1]. Inspired by these results we performed high-resolution thermal expansion and magnetostriction measurements on the half-metallic CMR material HgCr2Se4 [2], where the paramagnetic to ferromagnetic transition at 105K drives an insulator-to-metal transition with an 8-orders-of-magnitude decrease of the longitudinal resistivity (MR effect: 7·104 at 8T and 110K!). We will discuss the phenomenology of the coupling of charge and magnetic degrees of freedom to the lattice distortion and compare our results to other CMR materials. [1] Manna et al., PRL 113, 067202 (2014); [2] Guan et al., PRL 115, 087002 (2015)