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Coherent epitaxial Fe3O4 layers in the range of 0 to 400 Å have been grown by molecular beam epitaxy on single crystal MgO(100) substrates. The magnetic properties were studied by local magneto-optical Kerr effect experiments on a wedge shaped Fe3O4 layer, by ferromagnetic resonance and SQUID. The results show that the magnetic behavior of the Fe3O4 thin films resembles bulk Fe3O4 in the investigated thickness range.

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We present magnetoresistance (MR) data of high-vacuum magnetron sputtered NiFe/Cu multilayers (NiFe=Ni80Fe20) grown on Si(100) substrates with a Cu buffer layer and compare these with earlier results on Co/Cu(100) multilayers [1]. Measured MR values are directly proportional to the antiferromagnetically coupled fraction in the multilayers. Extrapolating to full antiparallel alignment, we can make a reliable comparison of the MR with the magnetoresistance model of Levy, Zhang, and Fert [2,3]. For the NiFe/Cu multilayers the deduced spin-asymmetry parameters are $$\alpha _i^{\text{NiFe/Cu}} = 5.0 \pm 0.4$$ and $$\alpha _b^{\text{NiFe}} = 2.1 \pm 0.3$$ for interface and bulk scattering, respectively. Although much smaller than in our Co/Cu multilayers, where $$\beta _i^{Co/Cu} = 21 + 3$$ and $$\alpha _b^{Co} = 2.6 + 0.3$$ , it is still the spin dependence of the interface scattering that is the main cause for the large MR values.

We have studied the effect of an artificially intermixed region grown at the interfaces of Co/Cu spin valves with uncoupled layers. Two different structures are used: exchange-biased spin valves and engineered spin valves in which two layers are antiferromagnetically coupled and a third layer, on top of this system, is not coupled to the other two. It is shown that structural effects, induced by variation of the deposition parameters and by the intermixing can play an important role. Since the present study uses sputtered layers an intrinsic initial intermixing of 4-5Å is already present. For both types of spin valves Gp, ΔG and ΔR/R all show a gradual decrease when the nominal thickness of the total intermixed region is enlarged from 0 to 36Å. Also when the initial degree of intermixing is decreased by sputtering at higher Arpressure, Gp, ΔG and ΔR/R still show a gradual decrease as a function of intermixed layer thickness. Combined with the fact that there is no difference between an intermixed region of thickness t at one Co/Cu interface or intermixed regions of thickness t/2 at two interfaces, this indicates that the electron scattering in the intermixed region is predominantly spin independent, although this region preserves a magnetic moment.

In this paper experimental evidence is presented for the carrier concentration dependence of the magnetic properties of Sn0.97Mn0.03Te, yielding a critical concentration above which ferromagnetic interactions are dominant. The observed behavior can be fairly well explained within a modified RKKY-model. Preliminary experiments on the low temperature magnetic phases indicate re-entrant spinglass behavior, which is qualitatively described with the spinglass model of Sherrington and Kirkpatrick.