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Dynamic heat capacity in Perovskite Manganites


Y. Jeong1

1Department of Physics, Pohang University of Science and Technology, Pohang, Korea

Keywords: dynamic calorimetry
property: magnetocaloric effect
material: metals oxides

We constructed an adiabatic calorimeter and a Peltier microcalorimeter [1], which allow the measurements of static and dynamic heat capacity of a solid, respectively. Using these calorimeters, we measured static and dynamic heat capacity of polycrystalline La1-xAxMnO3 samples (with x of about 0.3 and A = Ca, Sr, and Ba), which display a drastic change in the Curie temperature Tc depending on the radius of A-site cations. In particular, the system of A = Ca shows an extremely large heat capacity peak near Tc, and an associated large magnetocaloric effect. We demonstrate, from the dynamic heat capacity measurements, that the heat capacity of this material depends on the frequency of measurements in the vicinity of the phase transition and this is due to the inhomogeneous first-order nature of the magnetic transition. This first-order nature also accounts for the large magnetocaloric effect.

References
  1. I. K. Moon et al., Appl. Phys. Lett. 76, 2451 (2000); Thermochim. Acta 377, 1 (2001); Rev. Sci. Instrum. 77, 064901 (2006).

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