Dysprosium iron garnet Dy3Fe5O12 (DyIG) thin films have been synthesized by postoxidizing at a temperature Tox (400 °C<Tox<1100 °C) of rf sputtered amorphous Dy-Fe metallic films. The sputtering conditions strongly influence the growth, the composition and magnetic and magneto-optic properties of the oxidized films. Pure DyIG films, free of DyFeO3, are synthesized at Tox∼1000 °C. Magnetic and Faraday rotation (FR) experiments at three wavelengths (543.5, 632.8, and 1152 nm) were performed on DyIG films in the 4–300 K temperature range, as a function of magnetic field up to 20 kOe perpendicular to the film plane. Magnetization and FR data are in good agreement with results obtained on bulk DyIG materials. Temperature dependent coercivity is observed with a discontinuity in the vicinity of the compensation temperature (Tcomp∼225 K). The temperature variations of the spontaneous FR values for the three wavelengths are interpreted on the basis of contributions proportional to the magnetization of each sublattice.

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The effect of the annealing temperature a well as the antiferromagnetic (AF) and ferromagnetic (F) thickness on exchange coupling in Ni81Fe19/Mn single bilayers was systematically studied. We then show that a large exchange coupling is observed when the bilayers are annealed at 300 °C: it corresponds to an exchange field of about 290 Oe. This large exchange field is induced with a rather thick F layer of 46 nm. Both the exchange field Hex and coercive field Hc increase with Mn thickness reaching saturation around 100 nm of Mn. The exchange coupling is associated with interfacial diffusion at the NiFe/Mn interface. This result is confirmed by a large change in magnetization and resistivity before and after annealing. We show that the existence of the exchange field is associated with the clear evidence of a new FeMnNi phase in the x-ray spectrum.

Magnetic properties of the normal cubic spinel CdFe204 have been investigated on a single crystal above the spin-ordering temperature -10 K, in uniform applied magnetic fields 0 & H & 70 kG.Our measurements reveal the existence of a huge nonlinear magnetic susceptibility y"i up to room temperature, characteristic of disordered antiferromagnets in an applied field H. Our experimental results match those obtained previously on ZnFe204 in a field H =9.7 kG. We show that the nonlinearity is responsible for the anomalous magnetic properties incorrectly attributed to the existence of magnetic clusters associated with Fe ions in tetrahedral sites Fe(A) in the previous works. In the limit H~0, the magnetic susceptibility satisfies the Curie law for T & 30 K, with the Curie constant in quantitative agreement with the theoretical value for Fe + ions in the S5&2 state. We argue that the fraction x of Fe(A) ions, if any, is very smaH (x (10 ) so that the nonlinearity cannot be attributed to the site-dilution characteristics of random-field systems. Instead, it is attributable to the large frustration inherent in the topology of the normal spinel cubic lattice.