| Popis: |
On-line ultrasonic measurements on La 0.7 Sr 0.3 Mn 1− x Ni x O 3 perovskite manganite material ( x =0.01, 0.02 and 0.03) were performed on the samples synthesised by solid state reaction technique. The XRD studies on the samples confirm the crystalline nature with single phase rhombohedral structure having R3C space group. The average size of the particles determined using SEM images are 0.587, 0.412 and 0.356 µm for x =0.01, 0.02 and 0.03 respectively. The temperature dependent ultrasonic velocities and attenuation measurements on the samples were used to reveal the ferromagnetic to paramagnetic phase transition temperature (Curie temperature) 374, 358 and 342 K for the values of x =0.01, 0.02 and 0.03 respectively. In addition, ultrasonic measurements confirm that the increase in Ni doping concentration in La 0.7 Sr 0.3 Mn 1 − x Ni x O 3 perovskites leads to a decrease in Curie temperature. The change in Mn 3+ /Mn 4+ ratio with the phase transition temperature was explained on the basis of variation in amplitude of observed anomaly in ultrasonic measurements. The replacement of Mn 4+ ion by Ni 2+ ion leads to a change in the structural parameters and in the concentration of Mn 3+ and Mn 4+ ions. |
Full Text from ScienceDirect