K. V. Rao

Magnetic properties of Cr containing dilute concentrations of Co in the neighborhood of the Néel temperature

Magnetic susceptibility (χ) of Cr and Cr alloys continaing 1.7, 2.2, 2.7, 4.4 and 6.2 at.% Co have been measured as a function of temperature (T) between 300 and 600 K. Each of the χ vs T curves exhibits a well‐defined maximum at the Neel temperature (TN). Assuming that χ of the matrix is unchanged by small additions of solute, the magnetic susceptibility of Co (χCo) in Cr has been determined over the above‐mentioned T range. Above TN (except close to TN) χCo obeys the Curie‐Weiss law. The magnetic moment per Co atom decreased with increasing Co concentration. It has been found the χCo just above TN cannot be described by a power law with constant critical exponents.

Wiedemann-Franz Ratio of Magnetic Materials

We demonstrate that in magnetic materials there is enough evidence to show that some of the physical processes occuring at the onset of magnetic ordering strongly influence the electrical but not the thermal resistance. The observed anomalous behaviour of the Wiedemann-Franz ratio vs temperature is then simply a mathematical artifact manifesting the individual complicated temperature dependencies in the two resistivities. A new explanation for the observed anomalous Wiedemann-Franz ratio vs temperature for Cr, and analyses of the thermal and electrical resistivity data of Nd and Tb are given.

Thermal Conductivity of Cr-Rich Cr-Si Between 3 and 300 K

The Cr-Si system exhibits above about 1 at% Si a large first order antiferromagnetic transition which is not well understood so far. Simultaneous measurements of thermal conductivity λ and electrical resistivity ρ on two Cr-Si alloys of 0.9 and 1.4 at% Si in the temperature range 3-300 K have been carried out to gain further insight into the role of electronic and lattice properties at the magnetic transition at the Neel point TN. At TN a step-like change in λ was observed for the Cr-1.4 at% Si alloy while λ was almost featureless for the lower concentration. The Lorenz number L, which was found to lie in the range 4-7 WΩ deg-2, exhibits a broad peak centered around 60 K. Analysis of the λ-data reveals below 50 K a dominating lattice thermal conductivity term with a T2 dependence and decreasing in magnitude with increasing Si concentration. Around TN electronic contributions are found to dominate the thermal conductivity although both lattice and electronic effects seem to be responsible for the enhancement of L over the Sommerfeld value L0.

Abstract: Thermal and electrical properties of Cr+1.37 at% Si

We have carried out simultaneous thermal conductivity, λ, and ρ studies on an alloy of Cr+1.37 at% Si in the temperature range 4–300K. (AIP)

Electrical resistivity of Fe dissolved in PdAg matrix alloys

Abstract The temperature dependence of the resistivities of the system Pd1−xAgx up to x = 0.5, doped with 0.5, 1.0 and 2 at.% Fe has been measured. Clear reduction in the resistivities near the ferromagnetic and spin glass ordering temperatures are observed. The resistance minima observed in some of these alloys are discussed in terms of local s-d effects.

Pressure dependence of the magnetic transition in Cr-Si alloys

Abstract Our experimental determination of the pressure dependence of TN establishes that in Cr-alloys richer than about 1.38 at.% Si, the transition is to a commensurate phase. This can be rationalized only if Si acts as an electron donor to the Cr d-band and goes interstitially. At the first-order transition δS is estimated to be 0.007 cal/mol K.

Magnetic susceptibility measurements on Sm1−xGdxS(x = 0.15, 0.17, 0.18)

Abstract Magnetic susceptibility measurements have been performed on Sm 1− x Gd x S for x = 0.15, 0.17 and 0.18. The analysis of our data supports the view that while Gd simulates the pressure effects on SmS its localized moment has practically no influence on the phase transition.