We have investigated the magnetic properties of Fe 1−x Ni x -alloys for 13 different compositions ranging from pure Fe to pure Ni. The alloy series was prepared as thin films by co-deposition of Fe and Ni via ultra-high vacuum magnetron sputtering and the concentrations were determined by energy dispersive x-ray fluorescence analysis (EDX). The averaged magnetization and magnetic moment were measured at room temperature using a superconducting quantum interference device (SQUID) magnetometer and a vibrating sample magnetometer (VSM). Making use of x-ray magnetic circular dichroism (XMCD), the individual magnetic moments of Fe and Ni across the alloy concentration range were analyzed; thus their spin and orbital contributions were extracted. The weighted sum of the individual moments agrees very well with the average moments determined via SQUID and VSM. The Ni moment steadily increases from the pure Ni towards to the pure Fe range, while the Fe moment scatters around a value of about 2.4 μ B . Close to the invar composition of x = 0.35 we do not observe an anomaly of the magnetic moments, either of the individual moments or of the average moment. We also discuss different assumptions for the analysis of the XMCD spectra and assess the results in the light of recent theoretical predictions and literature values.

We have employed soft and hard x-ray resonant magnetic scattering and polarized neutron diffraction to study the magnetic interface and the bulk antiferromagnetic domain state of the archetypal epitaxial Ni 81 Fe 19 ͑111͒ / CoO͑111͒ exchange biased bilayer. The combination of these scattering methods provides unprecedented detailed insights into the still incomplete understanding of some key manifestations of the exchange bias effect. We show that the several orders of magnitude difference between the expected and measured value of exchange bias field is caused by an anisotropic in-plane orientation of antiferromagnetic domains. Irreversible changes in their configuration lead to a training effect. This is directly seen as a change in the magnetic half-order Bragg peaks after magnetization reversal. The antiferromagnetic domain size is extracted from the width of the ͑ 1 2 1 2 1 2 ͒ antiferromagnetic peak by both neutron and x-ray scattering and is determined to be 30 nm in size. A reduced blocking temperature as compared to the measured antiferromagnetic ordering temperature clearly corresponds to the blocking of antiferromagnetic domains. Moreover, an excellent correlation between the size of the antiferromagnetic domains, exchange bias field, and frozen-in spin ratio is found, providing a comprehensive understanding of the origin of exchange bias in epitaxial systems.

Abstract. We report on the element-resolved precessional dynamics of Fe magnetic moments in a homogeneous FeNi thin film. In our pump-probe experiment the magnetic system is excited by a magnetic field pulse from a stripline. The instantaneous response to the field pulse excitation is monitored as a function of time in a stroboscopic measurement using element selective X-ray Resonant Magnetic Scattering (XRMS). Our data show that Fe and Ni moments are aligned parallel to each other at all times, while they oscillate around the effective field direction given by the step field pulse and applied bias field. The field dependence of the precessional motion and damping of Fe magnetic moments is analyzed and compared to time-resolved Magneto-Optical Kerr Effect (tr-MOKE) measurement data from literature, showing good agreement. Additional studies proove the capability of our setup to conduct temperature dependent studies. In case of the presented FeNi system no changes in the frequency or damping behavior are observed within a temperature range of 150 − 350 K.

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A new set-up is presented to measure element-selective magnetization dynamics using the ALICE chamber [Grabis et al. (2003), Rev. Sci. Instrum. 74, 4048-4051] at the BESSY II synchrotron at the Helmholtz-Zentrum Berlin. A magnetic-field pulse serves as excitation, and the magnetization precession is probed by element-selective X-ray resonant magnetic scattering. With the use of single-bunch-generated X-rays a temporal resolution well below 100 ps is reached. The ALICE diffractometer environment enables investigations of thin films, described here, multilayers and laterally structured samples in reflection or diffuse scattering geometry. The combination of the time-resolved set-up with a cryostat in the ALICE chamber will allow temperature-dependent studies of precessional magnetization dynamics and of damping constants to be conducted over a large temperature range and for a large variety of systems in reflection geometry.