EPR studies of linewidth anomalies at phase transitions in [N(C2H5)4]2MnCl4

We have studied [N(C2H5)4]2MnCl4 crystal by X-band CW EPR spectra in the temperature range 170-300 K. The angular dependences of linewidth ΔH were measured and described in the light of a double-layer system (2D) with exchange interactions. Two temperature anomalies of linewidth ΔH were found at T1=225 K and T2=192 K on cooling. Different behaviors of ΔH anomalies recorded for an external magnetic field parallel and perpendicular to the ab crystallographic plane indicate ordering/disordering of MnCl4 groups in this plane and their displacement along the c-axis which occurs in the temperature of about 225 K.