Magnetotransport and acoustic effects in variable valence element-substituted manganese selenides

The magnetic, transport and acoustic properties of materials Tm X Mn 1−X Se (0.025 ≤ X ≤ 0.2) have been studied in magnetic fields of up to 12 kOe at temperatures of 80‒600 K. The magnetic phase transition temperatures (T N ) and change in the sign of resistance at DC current in vicinity of the T N were established. The temperature and concentration ranges corresponding to the maximum magnetoresistance (− 50% for X = 0.025) and magnetoimpedance (12% for X = 0.2) have been determined. The mechanism of relaxation has been established from the impedance spectrum and the activation energy change upon temperature and concentration has been found. The difference between the dc and ac magnetoresistances has been disclosed. The concentration range with hole and electron type carriers is determined. The mobility anomalies in the vicinity of the valence transition have been established. It is shown that the current and electrical resistance in the Tm X Mn 1−X Se compound can be manipulated by ultrasound and a magnetic field. A qualitative difference between the interaction of current and ultrasound in the magnetically ordered and paramagnetic regions is found.