Frustrated spin correlations in diluted spin ice Ho(2-x)La(x)Ti(2)O(7).

Journal of physics. Condensed matter : an Institute of Physics journal

PubMedID: 21694297

Ehlers G, Mamontov E, Zamponi M, Faraone A, Qiu Y, Cornelius AL, Booth CH, Kam KC, Toquin RL, Cheetham AK, Gardner JS. Frustrated spin correlations in diluted spin ice Ho(2-x)La(x)Ti(2)O(7). J Phys Condens Matter. 2008;20(23):235206.
We have studied the evolution of the structural properties as well as the static and dynamic spin correlations of spin ice Ho(2)Ti(2)O(7), where Ho was partially replaced by non-magnetic La. The crystal structure of diluted samples Ho(2-x)La(x)Ti(2)O(7) was characterized by x-ray and neutron diffraction and by Ho L(III)-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.