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R. G. Herb Condensed Matter Seminar
Formation of Magnetic Microphases in Ca$_3$Co$_2$O$_6$
Date: Monday, April 30th
Time: 4:30 pm
Place: 5310 Chamberlin
Speaker: Yoshitomo Kamiya, Los Alamos National Lab
Abstract: We study a frustrated quantum Ising model relevant for Ca$_3$Co$_2$O$_6$ that comprises a triangular lattice of weakly-coupled ferromagnetic chains. According to our quantum Monte Carlo simulations, the chains become ferromagnetic and form a three-sublattice "up-up-down'' structure below a temperature $T=T_{ ext{CI}}$. In contrast, long-period spin-density-wave (SDW) modulations along the chains are stabilized for $T_ ext{CI} < T < T_c$ in agreement with recent experiments by Agrestini et al [1]. Our mean field solutions reveal quasi-continuous change of the periodicity as a function of $T$, implying the existence of metastable states in the SDW phase that explains the very slow low-temperature dynamics that has been observed in Ca$_3$Co$_2$O$_6$ [2]. Closely related multiferroic materials Lu$_2$MnCoO$_6$ [3] and Ca$_3$MnCoO$_6$ [4] will also be discussed.

References:
[1] S. Agrestini et al., Phys. Rev. Lett., 101, 097207 (2008)
[2] T. Moyoshi and K. Motoya, J. Phys. Soc. Jpn., 80, 034701 (2011)
[3] S. Yanez-Vilar et al., Phys. Rev. B, 84, 134427 (2011)
[4] Y. J. Jo et al., Phys. Rev. B. 79, 012407 (2009)
Host: Perkins
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