Metamagnetism

About: Metamagnetism is a research topic. Over the lifetime, 2023 publications have been published within this topic receiving 38108 citations.

Magnetic and calorimetric studies of magnetocaloric effect in La0.7-xPrxCa0.3MnO3

Abstract: We report magnetocaloric effect in La0.7 − xPrxCa0.3MnO3 (x = 0, 0.2, 0.3, and 0.4). All these compounds undergo first-order paramagnetic to ferromagnetic transition upon cooling and show field-induced metamagnetic transition (FIMMT) in the paramagnetic state. The FIMMT is accompanied by a release of latent heat and change in temperature of the sample as evidenced from differential scanning calorimetry and thermal analysis data for x = 0.3. The magnetic entropy decreases (−ΔSm = 8.23, 8.1, 7, and 5.38 Jkg−1 K−1 for a field change of ΔH = 5 T, for x = 0, 0.2, 0.3, and 0.4, respectively) and refrigeration capacity (RC) increases with increasing x (RC = 197, 215, 240, and 259 J/kg for x = 0, 0.2, 0.3, and 0.4, respectively). We suggest that collapse of magnetic polarons in the paramagnetic state and magnetovolume effect are responsible for the observed FIMMT and large −ΔSm values.

Specific-Heat Anomaly around Metamagnetic Transition in UCoAl

Abstract: We have measured the specific heat and magnetocaloric effect of an UCoAl single crystal down to ∼0.1 K in fields applied along the c -axis to investigate the thermodynamic aspects of the metamagnetic behavior. Hysteresis behavior observed in both physical quantities below ∼3 K confirms the first order character of the metamagnetic transition. We have found that an apparent decrease of the electronic part of specific heat C e / T by 20% at 0.25 K with increasing field across the metamagnetic transition field of ∼1 T, evidencing the change in the density-of-states at the Fermi energy. C e / T gradually decreases with increasing temperature in zero field. This anomalous temperature dependence can be explained by taking into account a spin fluctuation contribution in the low-field state.

A change of the Fermi surface across the metamagnetic transition under pressure in UGe2

Abstract: We have performed the de Haas-van Alphen (dHvA) and ac-susceptibility experiments on a ferromagnet UGe2 under pressure for the field along the easy a-axis. The p-H phase diagram was determined, indicating three kinds of phase: paramagnetic and weakly and strongly polarized phases. The detected dHvA frequencies as well as the cyclotron masses are found to be very different between the weakly and strongly polarized states. A change of the Fermi surface occurs when the weakly polarized phase is changed into the strongly polarized phase with increasing magnetic field.

Magnetic instabilities in CeRu2Si2 compounds

Abstract: Neutron scattering experiments were recently performed in compounds of the CeRu2Si2 family. The topic addressed is the proximity of magnetic instabilities. The first one is the proximity of a T=0 K quantum phase transition experimentally achieved with lanthanum doping. The second kind of instability is linked to the competition between antiferromagnetic and ferromagnetic interactions in these materials. The pseudo-metamagnetic transition of CeRu2Si2 and the occurrence of an antiferromagnetic phase in the ferromagnetic compound CeRu2Ge2 were studied. Comparisons with macroscopic measurements are made using a simple analysis of the data.