Structural and Magnetic Phase Transitions in Minerals

antiferromagnetic appears applied approximation atoms axis Ballet behavior bond calculated cation Chem chemical cluster Coey components composition constant corresponding coupling critical crystal decreases density dependence described determined diffraction direction disordered Dolino effect electron energy equilibrium estimated et al exchange experimental experiments Fe2+ ferromagnetic field function Ghose give given heat ilvaite inc phase increases indicate interactions ions iron lattice layers Lindsley lower mantle magnetic magnetic order materials measurements Mineral mode Mössbauer natural neutron observed obtained occur octahedral olivines order parameter pairs perovskite phase diagrams phase transition Phys physical pigeonite polytypes positions possible potential predicted pressure properties pyroxenes quartz range respectively Salje sample shown shows silicates solid solution space group spin stability structure symmetry Table temperature theory thermodynamic tion transformation unit variation