Fluctuation-induced interactions and the spin-glass transition in Fe2TiO5

We investigate the spin-glass transition in the strongly frustrated well-known compound Fe2 TiO5. A remarkable feature of this transition, widely discussed in the literature, is its anisotropic properties: The transition manifests itself in the magnetic susceptibly only along one axis, despite Fe3+ d5 spins having no orbital component. We demonstrate, using neutron scattering, that below the transition temperature Tg = 55 K, Fe2 TiO5 develops nanoscale surfboard-shaped antiferromagnetic regions in which the Fe3+ spins are aligned perpendicular to the axis which exhibits freezing. We show that the glass transition may result from the freezing of transverse fluctuations of the magnetization of these regions and we develop a mean-field replica theory of such a transition, revealing a type of magnetic van der Waals effect.