V Felea et al 2011 J. Phys.: Condens. Matter 23 216001 doi:10.1088/0953-8984/23/21/216001
V Felea1,2, P Lemmens1, S Yasin3, S Zherlitsyn3, K Y Choi4, C T Lin5 and Ch Payen6
Show affiliationsThe magnetic phase diagram of multiferroic MnWO4 is studied in magnetic fields up to 60 T using sound velocity and sound attenuation measurements. Anomalies are observed at temperatures TN1 = 7.6 K, TN2 = 12.6 K and TN3 = 13.6 K that separate commensurate antiferromagnetic (AF1) to helical AF2 and commensurate AF3 to paramagnetic phases, respectively. The anomalies are significantly different and shed light on the spin–phonon coupling and evolution of the various order parameters in this multiferroic material. For temperatures below TN2 pronounced field hysteresis effects are also observed in the sound velocity, indicating field-induced transformations. In the temperature dependence of the attenuation we observe anomalies distinctively different from the usual maxima related to relaxation effects. They are attributed to the combination of dispersion effects due to domain walls and the discontinuously changing sound velocity. In total, six different magnetic phases, at various temperatures and fields including a novel high-field phase, are revealed and analyzed.
72.55.+s Magnetoacoustic effects
62.65.+k Acoustical properties of solids
75.30.Kz Magnetic phase boundaries (including magnetic transitions, metamagnetism, etc.)
Issue 21 (1 June 2011)
Received 24 February 2011, in final form 31 March 2011
Published 9 May 2011
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