Abstract

The direction of the magnetization of each Fe layer in an Fe/Cr multilayer with uniaxial anisotropy was determined with polarized neutron reflectometry. The vectors of the layer magnetization of the multilayer transit from an antiferromagnetic alignment into a nearly ferromagnetic one with increasing magnetic field. In the transition region the system consists of an antiferromagnetically aligned part and a ferromagnetically aligned part. The magnetization curve is characterized by the subsequent switching of the antiferromagnetically aligned bilayers into the nearly ferromagnetically aligned state. Via this mechanism the antiferromagnetic part of the multilayer reduces in favor of the ferromagnetically aligned part with increasing magnetic field.

Author Keywords: Polarized neutron reflectometry; Antiferromagnetic coupling; Layer magnetization

Article Outline

• References

(11K)
Fig. 1. Schematic presentation of the Fe/Cr multilayer sample with scattering geometry. Here, only four Fe layers are shown from the [Fe/Cr]_x12 structure. The sample has uniaxial in-plane anisotropy.

(10K)
Fig. 2. Magnetization curve of the Fe/Cr multilayer determined with VSM. The crosses indicate the magnetic field at which neutron reflectometry experiments were performed and what values of the net magnetization were obtained from the reflectivity data. The inset shows the uniaxial behavior of the sample measured at ~100 G.

(21K)
Fig. 3. Reflectivity curves (not corrected for polarization efficiency) taken from the Fe/Cr multilayer at various fields. The squares mark the measured (++) and (−−) spin configuration, respectively. (+) and (–) denote that neutron spin and magnetic field are parallel or antiparallel, respectively. The spin–flip scattering from the sample (±) and (±) are represented for (±) in the lower curve of each figure. The fit to the data (solid lines) includes the polarization efficiency of the polarizer and the analyzer. The reflectivity curves were measured at the magnetic fields: (a) H=20 G, (b) H=14 G, (c) H=450 G and (d) H=680 G.

(8K)
Fig. 4. Configuration of the layer magnetizations at five magnetic fields: (a) H=20 G, (b) H=14 G, (c) H=90 G, (d) H=450 G and (e) H=680 G. The presentation of the layer magnetizations with full and broken arrows helps to identify couples of anitiferromagnetically coupled layers and their transition to the ferromagnetic-like alignment.

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