Observation of Griffith like phase and large magnetocaloric effect in nanocrystalline La0.7Ag0.2Bi0.1MnO3

In this paper, we present structural, magnetic, magnetocaloric, and critical study of perovskite La0.7Ag0.2Bi0.1MnO3 (LABMO) nanocrystalline compound synthesized by the sol-gel method. Temperature dependent magnetization measurements reveal the significant suppression of ferromagnetism in the LABMO sample upon Bi-doping on a La-site. The downturn in inverse magnetic susceptibility (chi(-1)) observed just above T-C (236 K) in the paramagnetic regime corroborates the presence of short-range ferromagnetic correlations, which is the characteristic of the Griffith like phase below 270 K. The deviation from linear paramagnetic behavior in chi(-1) implies the strong Griffith singularity. Furthermore, we have employed an integrated Maxwell's thermodynamic relation numerically and used isothermal magnetization data to determine the change in magnetic entropy at various magnetic fields. For a magnetic field change of 5 T, the value of maximum magnetic entropy change is found to be similar to 6 J kg(-1) K-1. We have also explored the critical behavior of the LABMO sample at transition temperatures using different theoretical models. The value of exponents beta, gamma, and delta does not fall into any known universality class. Despite this, the scaling relations show that interactions are renormalized around the Curie temperature (T-C). The exponent n <= 2 extracted from field dependency on the magnetic entropy change confirms the second-order phase transition in LABMO. Published under an exclusive license by AIP Publishing.

Automated summary

In this paper, the structural, magnetic, magnetocaloric, and critical properties of perovskite La0.7Ag0.2Bi0.1MnO3 (LABMO) nanocrystalline compound synthesized by the sol-gel method are presented. It is found that the ferromagnetism in LABMO is significantly suppressed upon Bi-doping. The presence of short-range ferromagnetic correlations and the strong Griffith singularity are confirmed. The change in magnetic entropy at different magnetic fields is determined, and the critical behavior of LABMO at transition temperatures is explored using different theoretical models.