The reversible transverse susceptibility χt of a ferromagnet having a positive uniaxial anisotropy has been measured as a function of the applied magnetic field. The presence of peaks in the χt (H) curve of a polycrystal was predicted by theoretical calculations based on the Stoner and Wohlfarth model [A. Aharoni, E. M. Frei, S. Shtrikman, and D. Treves, Bull. Res. Counc. Isr. A 6, 215 (1957)]. Unlike previous measurements, our data verify the predictions of such a theory. An explanation for the failure of previous attempts to detect the peaks in the χt (H) curve is given. It is also experimentally shown that the χt (H) measurement allows a precise determination of both coercive and anisotropy fields in a uniaxial ferromagnet provided it is made by single domain particles.

Macroscopic magnetic measurements, Mössbauer, and neutron diffraction studies have been carried out on BaCoxZn2−xFe16O27 [(Zn−Co)2-W] single-crystal hexaferrites. The extrapolated saturation magnetization values σs(0) are slightly lower than those found in the literature. Such differences have been justified as due to the different Co and Zn distributions among the tetrahedral sites.The Co ions induce a strong planar contribution to the magnetic anisotropy. At low temperature, the spin order, found from the macroscopic magnetic measurements and preliminary neutron diffraction studies, is planar, while the Mössbauer data indicate a conical order with an angle of 70° with respect to the c axis. By increasing the temperature, the cobalt anisotropy decreases and a spin reorientation to easy axis is observed.

We report the existence and characterization of the stable ternary phase Tb3(Fe1-xTix)29. The structural characterization by X-ray powder diffraction is evidence for a monoclinic structure (P21/c space group) with refined lattice parameters a=10.583(1) AA, b=8.5116(7) AA, c=9.6736(9) AA and beta =97.018(5) degrees . A large magnetovolume effect has been observed in the volume thermal expansion at the order temperature Tc=455 K. The anisotropy has been measured by using the singular point detection technique. Two distinct anisotropy fields of relatively high intensity have been detected. The HA values measured at 6.4 T and 1.9 T at 293 K and both increase markedly with decreasing temperature. Below 200 K, the approach to saturation corresponding to the highest HA develops into a first-order magnetization process.

LaMn1−y3+Mny4+O3±d and La0.67R0.33Mn1−y3+Mny4+O3±d (R = Ca, Sr, Ba) phases were synthesized at 350°C by using very reactive, amorphous precursors obtained from the stoichiometric citrate solutions. The chemical process was optimized with respect to the solution concentration, pH, and additives. The precursor reactions were investigated as a function of the cation stoichiometry and the additive by simultaneous thermal and thermogravimetric analysis and X‐ray diffraction. The reaction pathway was found to be independent of the cation stoichiometry, but related to the acid or base additive. The annealing temperature was systematically increased in the 350–1200°C interval and the La0.67Sr0.33MnO3±d properties (i.e., crystal sizes, Mn average valence, Curie temperature, magnetization, magnetic susceptibility) were measured and found to vary consistently as a function of it.

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