A mutual inductance bridge to measure low frequency magnetic susceptibilities of magnetic materials has been constructed. Salient features of the bridge, which uses a variable mutual inductance simulated using operational amplifiers, the cryostat and the coil assembly are described in this paper. The apparatus has been employed for accurate measurement of superconducting transition temperatures and for sensitive detection of magnetic ordering transitions in liquid helium and liquid nitrogen temperature ranges respectively. The bridge has been calibrated to determine the static susceptibility of magnetic materials as a function of temperature.

In this paper, we describe the operation of a vacuum adiabatic calorimeter controlled by a Rockwell AIM 65 microcomputer, which is suitable for specific heat measurements in the temperature interval 4.2–300 K. The system measures and calculates the specific heat and the results are printed out on a thermal tape. The cryostat, the electronic circuitry and the software are described. Results obtained using a pulsed heat technique on a specimen of high purity copper are given and compared with values reported in the literature.

Normal state electrical resistivity of the Chevrel phase compounds of the type Cu_1.8Mo₆S_8−ySe_y, 0⩽y⩽8 and Cu_1.8Mo₆S_8−yTe_y, 0⩽y⩽4 is analysed on the basis of the generalized diffraction model which incorporates a postulate on electron-phonon interaction,viz phonons with wavelength exceeding the electron mean-free path are ineffective electron scatterers. Fit obtained by this model was found to be superior to other models based on the interbands-d scattering of electrons.

The specific heat of superconducting oxide compound, YBa₂Cu₃O_{7 −x}, is studied using a quasi-adiabatic calorimeter from 4.2 to 60 K. The analysis of the specific heat data below 15 K gives a value of 17 mJ/mole K² for the electronic heat capacity coefficient. The value ofθ_D(0) is determined to be 397±8 K. The variation ofθ_D with temperature was calculated in the temperature range 4.2 to 60 K.

Annealing dependence of the lattice parameter, resistivity, magnetoresistance and thermopower have been studied on Nd_0.7-Sr_0.33MnO₃ thin films deposited on LaAlO₃ and alumina substrates by pulsed laser ablation. Upon annealing at 800°C and 1000°C the lattice constant of the LaAlO₃ film tends toward that of the bulk target due to reduction in oxygen vacancies. This results in a metal-insulator transition at temperatures which increase with progressive annealing along with a decrease in the observed low temperature MR. Using a magnon scattering model we estimate the e_g bandwidth of the film annealed at 1000°C and show that the magnon contribution to the resistivity is suppressed in a highly oxygen deficient film and gains prominence only upon subsequent annealing. We also show that upon annealing, the polaron concentration and the spin cluster size increases in the paramagnetic phase, using an adiabatic polaron hopping model which takes into account an exchange dependent activation energy above the resistivity peak.

We report polarized Raman scattering in single crystals of Nd_0.7Sr_0.3MnO₃. The temperature dependence of the MnO₆ octahedral bending and stretching modes observed in the XX spectra points to the existence of local lattice distortions, possibly polarons. The XY spectra have been analyzed using a collision-dominated model, which allows the extraction of the carrier scattering rate.

We report here the low-temperature resistivity of the chemical solution deposited La_1−xCa_xMnO₃ (x=0.2, 0.3 and 0.33) thin films on LaAlO₃ substrates. The films were post-annealed in atmosphere at 850°C. The low temperature resistivity data has been studied in order to understand the nature of low-temperature conduction processes. The data showed T² dependence from 60 K to 120 K consistent with the single magnon scattering process. The deviation from this quadratic temperature dependence at low temperatures is attributed to the collapse of the minority spin band. The two-magnon and electron-phonon processes contribute to scattering of carriers in the temperature range above 120 K.