Exchange-bias instability in a bilayer with an ion-beam imprinted stripe pattern of ferromagnetic/antiferromagnetic interfaces

Abstract

We have investigated the magnetization arrangement in an in-plane stripe pattern with alternating exchangebias domains. The stripe pattern was produced by ion bombardment induced magnetic patterning, which changed locally the exchange-bias direction at the ferromagnet/antiferromagnet interface, but not the magnetic or antiferromagnetic properties of the Co 70 Fe 30 and Mn 83 Ir 17 layers, respectively. For the analysis of the magnetic domain structure evolution along the hysteresis loop we used a combination of experimental techniques: magneto-optical Kerr effect, Kerr microscopy, polarized neutron reflectometry, and off-specular scattering of polarized neutrons with polarization analysis. Instead of a perfect antiparallel alignment we found that the magnetization in neighboring stripes is periodically canted with respect to the stripe axis so that the net magnetization of the ferromagnetic film turns almost perpendicular to the stripes. At the same time the projection of the magnetization vector onto the stripe axis has a periodically alternating sign. The experimental observations are explained and quantitatively described within the frame of a phenomenological model, taking into account interfacial exchange bias, intralayer exchange energy, and uniaxial anisotropy. The model defines conditions which can be used for tailoring nano-and micro-patterned exchange-bias systems with different types of magnetic order.

Tunable exchange bias-like effect in patterned hard-soft two-dimensional lateral composites with perpendicular magnetic anisotropy

“…[1][2][3][4][5][6][7] Usually, these systems consist in arrays of structures, where the magnetic behavior is studied as a function of shape and/or structures density without changing the intrinsic magnetic properties. The use of magnetic lateral multilayers, i.e., extended films with a 1D lateral modulation of intrinsic magnetic properties, such as magnetic anisotropy, 8 saturation magnetization, 9 or exchange bias, 10 introduces an extra freedom degree, which should be useful in the development of forefront magnetic devices. The combination of different exchange coupled materials gives rise to many interesting phenomena in standard vertical multilayers such as standard exchange bias in antiferromagnetic/ferromagnetic systems 11,12 or isothermal field induced exchange bias effects in coupled ferromagnetic bilayers with orthogonal anisotropies.…”

Depth-resolved investigation of the lateral magnetic correlations in a gradient nanocrystalline multilayer

“…In the off-specular geometry, Q has one or two of its components lying in the sample plane, which allows to probe lateral correlations of the magnetization fluctuations on length scales ranging from several tens of m [21][22][23][24][25] down to the nm range. 26 Neutron scattering under grazing incidence with polarization analysis is a method of choice to determine lateral fluctuations in direction and modulus of the magnetization vector in devices relevant for magnetoelectronics, making it a unique probe, even compared to the powerful techniques of magnetic force microscopy, photoemission electron microscopy, and resonant x-ray magnetic scattering or dichroism, as a depth information is available, which is not the case for the other methods mentioned.…”

Controlled nucleation of topological defects in the stripe domain patterns of lateral multilayers with perpendicular magnetic anisotropy

“…Briefly, a magnetic lateral multilayer (MLM) is a continuous magnetic film with a lateral modulation of some relevant magnetic property, e.g., M S , 27,28 exchange bias, 29,30 or anisotropy. 31,32 PMA lateral multilayers (PMA-MLM) can be fabricated by introducing a periodic thickness modulation 26 through a nanostructuration process since the equilibrium stripe domain configuration is very sensitive to thickness variations.…”