Random site occupancy induced disordered Néel-type collinear spin alignment in heterovalent Zn2+–Ti4+ ion substituted CoFe2O4

Crystal structure and spin arrangements of CoZnxTixFe2−2xO4 and its relation to magneton number with Zn2+–Ti4+ substitution.

Magnetic Susceptibility of Pressed Powders of Some Rare-Earth Iron Garnets

The molar magnetic susceptibilities (χм) of spherical balls of rare-earth iron garnets REIG's, with RE = Y, Gd, Dy, Ho, Er and Yb, prepared from pellets pressed at pressures ranging from 2 to 8 × 107 kg m-2 , have been measured in the temperature range 300-900 K. It is found that χмα exp( - f), where f is the pore fraction of the pressed balls. It has also been observed that χм for a particular garnet at a fixed temperature increases from powder through pressed material to single crystal. REIG's reveal typical ferrimagnetic behaviour with the ferrimagnetic Curie temperature (Tc) lying in the range 550-570 K for single crystals. In general, for pressed material Tc increases linearly with density. The χм-1 vs, T variation has been analysed using molecular field theory. It has been found that for T ≫ Tc the magnetic ions behave as if they were almost free and yield a magneton number very close to their free ion value.

Notizen: High Temperature Magnetic Susceptibility of Light Rare-Earth Tungstates

This paper reports our results on the magnetic suscep­tibility (Χm) of light rare-earth (viz. Ce, Pr, Nd, Sm, Eu and Gd) tungstates in the temperature range of 300 to 900 K. As expected the variation of Χm with temperature obeys the Curie-Weiss law Χm = C/T - θ). The values of the Curie-constant (C), paramagnetic Curie temperature (θ) and magneton number (p) for the magnetic ions of these tungstates have been evaluated. The experimental p values are in good agreement with the theoretical values of p for these ions. Thus it is concluded that the magnetic (4f) electrons remain intact with the respective ions at high temperature and their participation in electrical conduction is improbable. Negative values of θ normally indicate anti- ferromagnetic ordering in these compounds at low tem­peratures; however in these tungstates the crystal field seems to be the prime reason for Curie-Weiss law behaviour and negative values of θ. The magnetic behaviour of light rare-earth tungstates in briefly discussed.

On the possibility of a thermal effect accompanying sudden changes in the magneton-numbers in CuCl2 and NiSO47 H2O

1. The temperature variation of the paramagnetic susceptibility of most of the solids follows the generalised Curie lawas found first by Kamerlingh Onnes and Weiss. This gives a linear relation between 1/ψ and T. The value of C is a measure of the atomic magnetic moment, and if this moment is expressed in terms of the Weiss magneton-number p, thenwhere CM is the value of C when ψ refers to a gram-molecule. The experimental results for a paramagnetic substance are usually expressed in terms of p and θ. Weiss (1), Foex (2), Cabrera and others have found that in some substances there are discontinuities in the slope of the 1/ψ, T curve. Thus Weiss (3) finds that magnetite above its Curie point shows several sudden changes in the 1/ψ, T curve, which he has interpreted as corresponding to the magneton-numbers p = 4, 5, 6, 8,10. Similarly, for cupric chloride (anhydride) Weiss (4) gives p= 9.2 and 10, for the temperature ranges — 140° to 20° and 20° to 500° respectively. Nickel sulphate (5) has also been found to possess a transition point at about — 113°, where the p value on cooling changes from 14.6 to 18.2.