No abstract

No abstract

No abstract

The crystal and magnetic structures of TlFeS 2 and TlFeSe 2 chalcogenides are studied by neutron diffraction in the temperature range 10-300 K. The investigated compounds feature monoclinic crystal sym metry with the C2/m space group. Antiferromagnetic ordering occurs in TlFeS 2 and TlFeSe 2 at the Néel tem perature T N = 210(5) and 295(5) K, respectively. The temperature dependences of magnetic moments, Fe-Fe bond lengths, and unit cell volume are established. The coefficients of thermal expansion for the paramag netic and antiferromagnetic phases are calculated.

The magnetic, structural, and vibrational properties of YMn 2 O 5 multiferroic have been studied by means of neutron, x-ray powder diffraction, and Raman spectroscopy at pressures up to 6 and 30 GPa, respectively. Application of high pressure, P > 1 GPa, leads to a gradual suppression of the commensurate and incommensurate antiferromagnetic (AFM) phases with a propagation vector q = (1/2,0,q z ∼1/4) and appearance of the commensurate AFM phase with q = (1/2,0,1/2). This observation is sharply contrasting to general trend towards stabilization of commensurate AFM phase with q = (1/2,0,1/4) found in other RMn 2 O 5 compounds upon lattice compression. At P ∼ 16 GPa a structural phase transformation accompanied by anomalies in lattice compression and pressure behavior of vibrational modes was observed. The comparative analysis of high-pressure and R-cation radius variation effects clarified a role of particular magnetic interactions in the formation of the magnetic states of RMn 2 O 5 compounds.