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Pressure studies on K2Cr8O16 using neutrons and muons

日時 2018年10月25日 (木) 16:30-
場所 理学研究科 C212
講師 Yasmine Sassa
(Uppsala University)

Materials with 1D-channels have interesting magnetic properties where the ground state is determined by the complex correlation of both intra and inter chain interactions. The title compound, K2Cr8O16, belongs to a series of quasi-1D compounds synthesized using a high- pressure/-temperature technique. The channels are formed by zig-zag Cr2O4 chains parallel to the c-axis and K cations occupying the center. This is one of the few compounds undergoing metal to insulator transition while maintaining a ferromagnetic order [1, 2], established by a Peierls transition [3]. Pressure dependent studies on this compound is fairly limited and the complete phase diagram of this compound is not fully resolved, especially the low temperature / high pressure region [4, 5].

In this seminar, I will make an introduction about the muon spin rotation/relaxation (muSR) technique and present zero field (ZF) and weak-transverse field (wTF) muSR data on K2Cr8O16 obtained under high pressure. The obtained paramagnetic (PM) to ferromagnetic (FM) transition temperature differs notably compared to previously published magnetization measurements. In detail, the PM to FM transition temperature as a function of pressure is determined from wTF measurements and from the ZF data we established a novel low temperature/high pressure transition between two different magnetically ordered states, which was determined to be FM and antiferromagnetic (AF), respectively. Finally, neutron/X-ray scattering measurements and theoretical modeling have recently been conducted in order to elucidate the detailed nature of the two magnetically ordered phases.

[1] K. Hasegawa, et al. PRL 103, 146403 (2009)
[2] J. Sugiyama, et al. PRB 85, 214407 (2012)
[3] T. Toriyama, et al. PRL 107, 266402 (2011)
[4] O. K. Forslund, Y. Sassa, et al. JPS Conf. Proc. 21, 011006 (2018)
[5] O. K. Forslund, Y. Sassa, et al. submitted to Scientific Reports (2018)

問合せ先 Eike F. Schwier(放射光科学研究センター)