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What is magnetocaloric effect?
When magnetic field processed adiabatically, as a response of this magnetocaloric material shows large distinguished response for change in thermal content around the phase transition temperature due to a strong connection between magnetic and structural degree of freedom. This phenomenon can be visualize more specifically via the schematic representation of magnetic and lattice subsystem as shown in fig.1. When magnetic field is applied on magnetocaloric material, the magnetic are decreased due to processing the spin orientation, and material is forced to sustain at constant temperature via the heat exchange with reservoir. The entropy associated with spin state can be achieved adiabatically by changing magnetic field, total entropy of MCM system remains unaltered. This happens due to simultaneous reconciliation of entropy associated with the spin ordering and followed lattice deformation that assists a cahnge in lattice entropy. The lattice deformation spontaneously (and adibatically) raises the temperature of magneto-caloric specimen in order to compensate the loss of entropy due to spin orientation.
Figure 1: Schematic representation of magnetocaloric response against the field cycling.
Figure 2: Series of isothermal magnetization curve in the vicinity of magnetic transition temperature.
Figure 3: (a) Isothermal magnetization of typical ferromagnet, (b) Entropy curve
Figure 4: Phase diagram estimated from magnetocaloric behaviour.
Figure 5: Evolution magnetic phases and Magnetocaloric response.
Figure 6: Evolution of spin assisted elastic phase.
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