Study Of Magnetocaloric Effect Research Articles

Magnetocaloric effect in polycrystalline (La 0.5Gd 0.2)Sr 0.3MnO 3

In this paper, we present a study of magnetocaloric effect in the colossal magnetoresistance material (La 0.5Gd 0.2)Sr 0.3MnO 3. From the measurements of isothermal magnetization at different temperatures, we have discovered a large magnetic entropy change with a broad peak around Curie temperature (270.5 K) in (La 0.5Gd 0.2)Sr 0.3MnO 3 polycrystalline sample. Moreover, the maximum of magnetic entropy change exhibits a nearly linear dependence with applied high magnetic field. These results suggest that this material is a suitable candidate as working substance in magnetic refrigeration near room temperature.

Large magnetic entropy change above 300 K in La 0.67Sr 0.33Mn 0.9Cr 0.1O 3

In this paper, we present a study of magnetocaloric effect in the Cr-doped colossal magnetoresistance material La 0.67Sr 0.33MnO 3. From the measurements of isothermal magnetization at different temperatures, we have discovered a large magnetic entropy change at Curie temperature (328 K) in La 0.67Sr 0.33Mn 0.9Cr 0.1O 3 ceramic sample. The magnetic entropy change under 6 T magnetic field is ∼5.8 J/kg K, which suggests the studied material a possible candidate as working substance in magnetic refrigeration above room temperature.

Specific heat and magnetocaloric effect study of multiple field-induced phase transitions inHoGa2

Both temperature and field dependences of specific heat C and magnetocaloric effect (MCE) were measured on a ${\mathrm{HoGa}}_{2}$ single crystal in fields up to 8 T at low temperatures down to 0.1 K. The magnetic fields were applied in the [100] direction, for which intermediate magnetic phases appear. Significant Ho nuclear contribution to C is found to dominate below 1 K and its field-independent character reveals that the value of Ho magnetic moments does not change visibly in the measured field range irrespective of the magnetic phases. From anomalies observed in the C and MCE data, the reported field-vs-temperature phase diagram is corroborated thermodynamically. One of the phase transitions occurring at ${T}_{t}=6.6 \mathrm{K}$ in zero field is found to be of first-order transition. Magnetic entropy determined by the MCE measurements shows an enhancement in the intermediate phases and small humps at the phase boundaries. Based on a crystalline-electric-field model, the nuclear specific heat, magnetic entropy of the $4f$ electrons, and anisotropy in the magnetization can be explained consistently. Possible origins of the reported giant magnetoresistance caused by the appearance of the intermediate phases will be discussed.

Large magnetic entropy change in the colossal magnetoresistance material La 2/3Ca 1/3MnO 3

In this paper, we present a study of magnetocaloric effect in the colossal magnetoresistance material La 2/3Ca 1/3MnO 3. From the measurements of temperature dependence of magnetization under various magnetic fields, we have discovered a large magnetic entropy change associated with the ferromagnetic–paramagnetic transition. This result suggests that perovskite manganites are suitable candidates as working substances in magnetic refrigeration technology.

A study of magnetocaloric effect in PrCo 2Si 2 to understand contributions to magnetoresistance

The results of electrical resistivity and heat capacity measurements in the presence of an external magnetic field on the compounds PrCo 2Si 2 and Pr 0.8La 0.2Co 2Si 2 are reported. The magnetocaloric effect Δ T ad (Δ H, T) is obtained from in-field heat capacity data. Comparison has been made between the temperature dependence of Δ T ad and the change in resistance due to magnetic field Δ ρ [={ ρ( H)− ρ(0)}] in both the compounds. The study indicates that Δ T ad and −Δ ρ have similar temperature dependence where Δ ρ is predominantly due to the change in conduction electron relaxation time, but it may be different if it is dominated by the change in carrier concentration. This observation indicates the importance of magnetocaloric studies to understand the major contributions to magnetoresistance. The studies also indicate that a large positive magnetoresistance can be observed due to the appearance of a magnetic superzone gap with the application of an external magnetic field.

Magnetocaloric effect in La 1− xSr xCoO 3 (0.05⩽ x⩽0.40)

We report studies of magnetocaloric effect in lanthanum cobaltate doped with different Sr-concentrations, La 1− x Sr x CoO 3 (0.05⩽ x⩽0.4). The study has revealed that La 0.6Sr 0.4CoO 3, which exhibits a moderately large value of maximum entropy change of about 1.45 J/kg/K in 1.5 T DC-field around its Curie temperature (of 235 K), can be used as an active magnetic refrigerant (AMR) material at ∼235 K.