Magnetic ordering in the three-dimensional frustrated Heisenberg model

High-Temperature Ferroic Glassy States in SrTiO_{3}-Based Thin Films

Disordered ferroics hold great promise for next-generation magnetoelectric devices because their lack of symmetry constraints implies negligible hysteresis with low energy costs. However, the transition temperature and the magnitude of polarization and magnetization are still too low to meet application requirements. Here, taking the prototype perovskite of SrTiO_{3} as an instance, we realize a coexisting spin and dipole reentrant glass states in SrTiO_{3} homoepitaxial films via manipulation of local symmetry. Room-temperature saturation magnetization and spontaneous polarization reach ∼ 10  emu/cm^{3} and ∼ 25  μC/cm^{2}, respectively, with high transition temperatures (101 K and 236 K for spin and dipole glass temperatures and 556 K and 1100 K for Curie temperatures, respectively). Our atomic-scale investigation points out an underlying mechanism, where the Ti/O-defective unit cells break the local translational and orbital symmetry to drive the formation of unusual slush states. This study advances our understanding of the nature of the intricate couplings of ferroic glasses. Our approach could be applied to numerous perovskite oxides for the simultaneous control of the local magnetic and polar orderings and for the exploration of the underlying physics.

A TDPAC study of static and dynamic magnetic behaviour

The a-FexHf100-x system is used to explore the application of TDPAC (the time differential perturbed γ-γ angular correlation technique) to non-trivial anisotropic magnetic relaxation. The effect of fluctuations in this system is primarily to cause a decay of the zero-frequency component, which is characterized by the phenomenological decay rate λ. The zero-field magnetic phase diagram, constructed from both static and dynamic features of the data, and the temperature dependence of λ are both fully consistent with the physics of partial bond frustration. The results demonstrate that the magnetic fluctuations are meaningfully characterized by simple spectrum features, and are not obscured by large static fields or severe disorder.

Spin dynamics in a frustrated magnet

180 degrees spin flips have been identified as the dominant fluctuation mechanism at the transverse spin freezing transition in partially frustrated a-Fe92Zr8. The form of the selective excitation double Mössbauer spectra, coupled with the perfect agreement with zero-field muon spin relaxation data, eliminates other relaxation forms.