Spin relaxation in dipolar spin ice Dy$_{2}$Ti$_{2}$O$_{7}$ and Ho$_{2}$Ti$_{2}$O$_{7}$ was investigated using the magnetocaloric effect and susceptibility. The magnetocaloric behavior of Dy$_{2}$Ti$_{2}$O$_{7 }$at temperatures where the orientation of spins is governed by ``ice rules`` (T $<$ T$_{ice})$ revealed thermally activated relaxation; however, the resulting temperature dependence of the relaxation time is more complicated than anticipated by a mere extrapolation of the corresponding high temperature data [1]. A susceptibility study of Ho$_{2}$Ti$_{2}$O$_{7 }$ was performed at T $>$ T$_{ice }$and in high magnetic fields, and the results suggest a slow relaxation of spins analogous to the behavior reported in a highly polarized cooperative paramagnet [2]. [1] J. Snyder et al., Phys. Rev. Lett. 91 (2003) 107201. [2] B. G. Ueland et al., Phys. Rev. Lett. 96 (2006) 027216.
*Work supported by ESF-RNP-HFM, NSF DMR-0701400.
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Authors
Martin Orendac
Centre Low Temp. Phys., P. J. Safarik Univ. and SAS, Kosice, Slovakia
P. J. Safarik University and Inst. Exp. Physics SAS, Kosice, Slovakia
Lucia Sedlakova
P. J. Safarik University and Inst. Exp. Physics SAS, Kosice, Slovakia
Alzbeta Orendacova
Centre Low Temp. Phys., P. J. Safarik Univ. and SAS, Kosice, Slovakia
P. J. Safarik University and Inst. Exp. Physics SAS, Kosice, Slovakia
Peter Vrabel
P. J. Safarik University and Inst. Exp. Physics SAS, Kosice, Slovakia
Alexander Feher
Centre Low Temp. Phys., P. J. Safarik Univ. and SAS, Kosice, Slovakia
Centre of Low Temp. Physics, P. J. Safarik Univ. and Inst. Exp. Physics SAS, Kosice, Slovakia
P. J. Safarik University and Inst. Exp. Physics SAS, Kosice, Slovakia
