Ferromagnetic - spin glass transition induced by pressure in the geometrically frustrated pyrochlore (Tb$_{1-x}$La$_x$)$_2$Mo$_2$O$_7$

A. Apetrei; I. Mirebeau; I. Goncharenko; D. Andreica; P. Bonville

paper

Ferromagnetic - spin glass transition induced by pressure in the geometrically frustrated pyrochlore (Tb $_{1 - x}$ La $_{x}$ ) $_{2}$ Mo $_{2}$ O $_{7}$

arXiv:cond-mat/0604627

Abstract

We have studied (Tb $_{1 - x}$ La $_{x}$ ) $_{2}$ Mo $_{2}$ O $_{7}$ pyrochlores by neutron diffraction and $μ$ SR at ambient and under applied pressure. Substitution of Tb for La expands the lattice and induces a change from a spin-glass like state ({\itshape x}=0) to a non collinear ferromagnet ({\itshape x}=0.2). In the ferromagnetic structure, the Tb moments orient close to their local anisotropy axis as for an ordered spin ice, while the Mo moments orient close to the net moment. The $μ$ SR dynamical relaxation rate shows a cusp-like peak at the Curie temperature T $_{C}$ and a broad anomaly at T $^{⋆}$ $<$ T $_{C}$ , suggesting a second transition of local or dynamical nature. Under pressure, the long range order breaks down and a spin glass-like state is recovered. The whole set of data provide a microscopic picture of the spin correlations and fluctuations in the region of the ferromagnetic-spin glass threshold.

4 pages, 4 figures

Ferromagnetic - spin glass transition induced by pressure in the geometrically frustrated pyrochlore (Tb1−x​Lax​)2​Mo2​O7​

Abstract

Ferromagnetic - spin glass transition induced by pressure in the geometrically frustrated pyrochlore (Tb $_{1 - x}$ La $_{x}$ ) $_{2}$ Mo $_{2}$ O $_{7}$