Spin dynamics and magnetic phase transitions in quasi-two-dimensional antiferromagnet Mn[C10H6(OH)(COO-)]2x2H2O

The angular and frequency dependences of absorption line width in the EPR spectrum of the antiferromagnet Mn[C10H6(OH)(COO-)]2x2H2O are studied at high temperature (250 K). The EPR spectrum behaviour at high temperatures is described by the diffusion model for quasi-two-dimensional magnetic structures. The diffusion constant D, the starting time τ1 and the end time of the diffuse process τ2 are estimated. A nondiffusive contribution to the line width of the EPR spectrum was determined. The temperature and field dependences of magnetic susceptibility and magnetization are studied in a temperature range 1.8-25 K at impulse magnetic fields up to 150 kOe along the principal magnetic axes. A weak ferromagnetic moment is detected along the easy axis direction of Mn[C10H6(OH)(COO-)]2x2H2O. The spin-reorientations magnetic phase transitions are observed at H1=5 kOe (spin-flop transition) and at H2 ∼ (97±2) kOe and H3 ∼ (100±2) kOe (spin-flip transition) along the easy and mean magnetic axes