The effects of cubic crystal fields on the saturation magnetic moment of Sm³⁺ ion in ferromagnetic compounds have been investigated. In samarium compounds with magnetic elements, the exchange fieldH_ex acting on Sm³⁺ ion is taken to be proportional to the sublattice magnetization of the magnetic element, while in compounds with nonmagnetic elementsH_ex is taken to be proportional to the spin average of the Sm³⁺ ion and is determined self-consistently. In both types of compoundsH_ex is assumed to be along [001] direction. The saturation magnetic moment is calculated by taking into account the admixture of excited (J=7/2 andJ=9/2) levels into the ground (J=5/2) level of Sm³⁺ ion by crystal fields and exchange fields. It is shown that depending upon the strength, the crystal fields quench or enhance the magnetic moment from the free ion value, and in some cases force Sm³⁺ ion to behave effectively like an (L+S) ion rather than an (L−S)ion. The crystal fields may have important bearing on the performance of samarium compounds as permanent magnet materials.

Compounds of the formula RPd₃B_x (R=rare earth with 0⩽x⩽1) and RPd₃Si_x (R=La, Ce, Eu with 0⩽x⩽0.3) can be prepared by alloying boron or silicon with parent RPd₃ compounds. Addition of boron (silicon) does not change the structure but results in lattice expansion. The valence state of Ce in CePd₃ and that of Eu in EuPd₃ is strongly influenced by boron and silicon. Ce is known to be in a valence fluctuating state in CePd₃ while Eu is trivalent (J=0) in EuPd₃. The increase in the lattice parameter as a function of boron concentration is observed to be larger in CePd₃B_x and EuPd₃B_x compared to that in other RPd₃B_x alloys giving the first indication of the change in the valence state of Ce and Eu. This is confirmed from susceptibility measurements. With the addition of boron, susceptibility increases and the effective paramagnetic moments approach the values corresponding to Ce³⁺ (J=5/2, μ_eff=2.54 μ_B) and Eu²⁺ (J=7/2, μ_eff=7.94 μ_B) in the two alloy systems CePd₃B_x and EuPd₃B_x respectively. In the case of europium alloys,¹⁵¹Eu Mössbauer studies point out the importance of near-neighbour environment effects. Further, in EuPd₃B, where all the europium ions are crystallographically equivalent, a single Mössbauer line, with an isomer shift characteristic of europium ions in valence-fluctuating state, is observed at 300 K. However, at 88 K the Mössbauer absorption splits into two lines corresponding to europium ions in two valence states,e.g. divalent- and trivalent-like. Such a behaviour indicates thermally-induced charge ordering of europium ions. Addition of silicon to CePd₃, like boron, results in unusual lattice expansion and changes the valency of cerium towards 3⁺. the valence change is further corroborated by susceptibility measurements. In EuPd₃Si_x alloys, susceptibility and Mössbauer studies indicate that in the limiting single phase alloy EuPd₃Si_0.25 the europium ions are on the verge of valence instability. Susceptibility results on CeRh₃B_x alloys are also presented.

Superconducting oxide-copper monoliths have been fabricated by shock-wave loading using cylindrical and plane geometries. Bulk densities up to 96% T.D. have been obtained by varying detonation parameters. The superconducting properties, interface bonding and microstructure of the compacts have been evaluated.

A comparison has been made of irreversibility temperature determined by four different methods in few specimens of lead (type-I) and niobium (type-II). The merger ofM_ZFC(T) andM_FC(T) curves giveT_r(H) values lower than those evident from vanishing the hysteresis in isothermal DC magnetization. The identification of peak temperature inx″_H(T) data withT_r(H) is appropriate only if the contribution from changes in the normal state electrodynamics can be isolated and the peak is narrow. The appearance of differential paramagnetic effect inx′_H(T) data is adequate to imply reversibility, however, its efficacy to precisely locate irreversibility line remains to be established.