A comparison of the local magnetic susceptibility in rare earth pyrochlores

Abstract

We report transverse field muon spin rotation studies of the rare earth pyrochlores Gd 2 Ti 2 O 7 and Tb 2 Ti 2 O 7 : The paramagnetic shift in the observed precession frequency depends on the local spin susceptibility and probes the contact hyperfine and dipolar fields at the muon site within these materials. The results are compared with measurements of the bulk susceptibility. While no features associated with magnetic ordering are observed down to 0:015 K; hysteretic behavior develops in Tb 2 Ti 2 O 7 below T ¼ 1 K; likely due to the formation of clusters of ferromagnetically correlated spins. r 2002 Elsevier Science B.V. All rights reserved. 0921-4526/03/$ -see front matter r 2002 Elsevier Science B.V. All rights reserved. PII: S 0 9 2 1 -4 5 2 6 ( 0 2 ) 0 1 6 7 1 -X

Crystal field and magnetoelastic interactions in Tb2Ti2O7

“…Among titanates RE 2 Ti 2 O 7 , of most interest is terbium titanate Tb 2 Ti 2 O 7 , in which the magnetic long-range order does not manifest itself at least to a temperature of 15 mK [2], whereas, in accordance with calculations, the phase transition from the paramagnetic to an antiferromagnetic state should have occurred at a temperature of 1.8 K [3]. Interestingly, an external pressure induces a long-range magnetic order in Tb 2 Ti 2 O 7 : under a pressure of 8.6 GPa at temperatures below 2.1 K, apart from the spin-liquid phase, an antiferromagnetic order with a complex magnetic structure is observed [4,5].…”

“…The parameters of the electron-deformation interaction characterize changes in the crystal field that are caused by both macroscopic and microscopic (due to displacements of sublattices) homogeneous deformations of the specimen. The obtained set of parameters is refined based on analysis of data available in the literature on measurements of spectra of inelastic scattering of neutrons, spectra of Raman light scattering, field dependences of the forced magnetostriction, and temperature dependences of elastic constants of Tb 2 [21]. The local point symmetry group of the rare-earth ion is the trigonal group…”

Optical spectroscopy ofYb2Ti2O7andY2<

“…The ground state of the spin system, corresponding to these spin-ice structures (similar to proton configurations in the ordinary hexagonal ice), is macroscopically degenerate. The long-range magnetic order is absent in Tb 2 Ti 2 O 7 , Ho 2 Ti 2 O 7 , Dy 2 Ti 2 O 7 down to 15 mK, [8][9][10][11] 46 mK, 12,13 and 60 mK, 14 respectively. At low temperatures, the spin freezing was observed with specific spin correlations and a local short-range order.…”

Critical slowing down in the geometrically frustrated pyrochlore antiferromagnet Gd2Ti2O7

“…In Gd 2 Ti 2 O 7 A hf = 18.9(2) mT/µ B from transverse-field µSR experiments at high temperatures [12]. In the magnetically ordered state, where Gd moments are oriented parallel to local 111 directions [8], two muon frequencies, 21.2(1) mT/µ B and 27.7(1) mT/µ B (assuming an ordered Gd 3+ moment of 7 µ B ), are observed in zero applied field [9].…”