Evolution of the inverse magnetocaloric effect for random-field to spin-glass crossover in SmCaCoMnO6-SmMnO3 nanocomposite

We observe an enhancement of inverse magnetocaloric effect (MCE) in SmCaCoMnO6 (94%) and SmMnO3 (6%) nanocomposite due to uniform external field-induced random field (RF) to spin glass (SG) crossover. RF is generally observed in diluted antiferromagnet and dilute dipole-coupled Ising ferromagnet systems. Under the application of magnetic-field (H), such systems may show a crossover from RF to SG at low temperatures (T). Here, we report a similar type of crossover but in ferrimagnetic SmCaCoMnO6 and antiferromagnetic SmMnO3 nanocomposite. A model of site dilution of the ferrimagnetic phase by the embedded antiferromagnetic regions is proposed. In this composite system, the RF appears at T < 35 K, which shows a crossover to SG at T < 15 K under the applied field. The enhanced inverse MCE (with an entropy change, -Lambda S-M similar to -0.95 J Kg(-1) K-1 for a change in H similar to 70 kOe at T similar to 7.5 K) due to the SG state is the consequence of field-induced RF-SG crossover giving highly H-dependent -Delta S-M in the SG regime, a requisite for large MCE.

Automated summary

We observed an enhancement of inverse magnetocaloric effect (MCE) in SmCaCoMnO6 (94%) and SmMnO3 (6%) nanocomposite due to the crossover from random field (RF) to spin glass (SG) under external magnetic field. This crossover is usually observed in diluted antiferromagnet and dilute dipole-coupled Ising ferromagnet systems, but in our study, it occurs in a ferrimagnetic and antiferromagnetic nanocomposite. The enhanced inverse MCE is the result of the field-induced RF-SG crossover, which leads to highly H-dependent ΔS in the SG regime.