J. P. Carlo, J. P. Clancy, K. Fritsch, C. A. Marjerrison, G. E. Granroth, J. E. Greedan, H. A. Dabkowska, B. D. Gaulin
The geometrically frustrated double perovskite Ba2YRuO6 has magnetic 4d3 Ru5 ions decorating an undistorted face-centered cubic (FCC) lattice. This system has been reported to exhibit commensurate long-range antiferromagnetic order below T_N = 36 K, a factor f ~ 15 times lower than its Curie-Weiss temperature \Theta_CW = -522 K. We report new time-of-flight neutron spectroscopy of Ba2YRuO6 which shows the development of a ~5 meV spin gap at the [100] magnetic ordering wavevector, coincident with the transition to long-range order. We also report spin waves extending to ~14 meV, a surprisingly small bandwidth in light of the large \Theta_CW for this system. We compare the spin gap and bandwidth to relevant neutron studies of the isostructural 4d1 system Ba2YMoO6, and discuss the results in the framework of relatively strong spin-orbit coupling expected in 4d magnetic systems.
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http://arxiv.org/abs/1304.3649
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