Inverse Magnetocaloric Effect and the Magnetostructural Transition in Pr_0.15Ca_0.85MnO₃ Manganite

Magnetic and magnetocaloric properties of electron-doped Pr _0.15 Ca _0.85 MnO ₃ (orthorhombic space group Pnma, no. 62, oP 20) manganite have been studied. Low field magnetization measurements suggest that the sample orders antiferromagnetically at 147 K ( $T_{N}$ ). Magnetocaloric effect (MCE) has been estimated in terms of isothermal magnetic entropy change ( $\Delta S_{m}$ ) and the maximum $\Delta S_{m}$ value is about 6.4 Jkg ⁻¹ K ⁻¹ at 137.5 K for 70 kOe field change. Low-temperature powder X-ray diffraction studies reveal a change from orthorhombic (space group Pnma , no. 62, oP 20) crystal structure to monoclinic (space group $P 2_{1}/m$ , no. 11–2, mP 20) structure below 140 K. The inverse MCE shows a maximum value around the magnetostructural transition temperature. Electrical resistivity and electron paramagnetic resonance (EPR) spectroscopy results reveal hopping conduction in the paramagnetic state.