G Ehlers et al 2008 J. Phys.: Condens. Matter 20 235206 doi:10.1088/0953-8984/20/23/235206
G Ehlers1, E Mamontov1, M Zamponi1,2, A Faraone3,4, Y Qiu3,4, A L Cornelius5, C H Booth6, K C Kam7, R Le Toquin7, A K Cheetham7 and J S Gardner4,8
Show affiliationsWe have studied the evolution of the structural properties as well as the static and dynamic spin correlations of spin ice Ho2Ti2O7, where Ho was partially replaced by non-magnetic La. The crystal structure of diluted samples Ho2−xLaxTi2O7 was characterized by x-ray and neutron diffraction and by Ho LIII-edge and Ti K-edge extended x-ray absorption fine structure (EXAFS) measurements. It is found that the pyrochlore structure remains intact until about x = 0.3, but a systematic increase in local disorder with increasing La concentration is observed in the EXAFS data, especially from the Ti K edge.
Quasi-elastic neutron scattering and ac susceptibility measurements show that, in x≤0.4 samples at temperatures above macroscopic freezing, the spin–spin correlations are short ranged and dynamic in nature. The main difference with pure spin ice in the dynamics is the appearance of a second, faster, relaxation process.
Issue 23 (11 June 2008)
Received 5 March 2008, in final form 6 March 2008
Published 30 April 2008
G Ehlers et al 2008 J. Phys.: Condens. Matter 20 235206
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