Results of the experimental investigations of magnetocaloric effect (MCE) and magnetostriction in Pr0.7Sr0.2Ca0.1MnO3 manganite in the temperature range of 80–310 K and in magnetic fields up to 80 kOe are presented. The behavior of the MCE is characteristic of materials with magnetostructural phase transitions of the first order. Frequency (1–14 Hz) dependences of the MCE in a magnetic field of 6.2 kOe are investigated. It is shown that near TC, the ΔT dependence of the frequency f is well described by the expression: ΔT(f)=ΔTf=0−Bfn (n = 1.53, B = 0.01185 K/Hzn). The results of the investigation of magnetostriction show that near TC, the value of magnetostriction is Δɛ = 4.49 ⋅ 10−4 in a magnetic field of 80 kOe. According to the results of the study of magnetostriction in various magnetic fields, it is shown that the change in the magnetic entropy is directly proportional to magnetostriction ΔSM = γ1Δɛ (γ1 = 2 ⋅ 104 J/kg K). This ratio can serve as another indirect method for estimating the MCE, which shows good agreement with the data of direct caloric measurements.

A microscopic theory of a single hydrogen centre embedded in a Niobium crystal lattice is given. The electronic structure is investigated on the basis of a special energy difference procedure devel­oped by Wahl et al. This procedure, here applied in its lowest approximation, yields the change in the electronic energy and electronic density distribution due to the embedded hydrogen atom. From these quantities, the dipole force tensor, the displacement of the ions close to the interstitial (nearest and next nearest neighbours) and the heat of solution are calculated. The computed results show good agreement with experimental data.

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