M. Wolff

Origin of the reduced exchange bias in an epitaxial FeNi(111)/CoO(111) bilayer

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

Competing magnetic interactions in exchange-bias-modulated films

{\text{Ni}}_{81}{\text{Fe}}_{19}(111)/\text{CoO}(111)

Structural characterization and magnetic profile of annealed CoFeB/MgO multilayers

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

Slip and depletion in a Newtonian liquid

(\frac{1}{2}\frac{1}{2}\frac{1}{2})

Scientific Reviews :3He Spin Filter at the Institut Laue-Langevin: Polarization Analysis of Diffuse Scattering

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.

Quantum states of neutrons in magnetic thin films

The magnetization reversal in stripelike exchange-bias-patterned

Structure and magnetism of Co2 MnGe–Heusler multilayers with V, Au and AlOx spacer layers

{\text{Ni}}_{81}{\text{Fe}}_{19}/\text{IrMn}

The influence of weak links on magnetic ordering in layered structures

thin films was investigated by complementary inductive and high-resolution magneto-optical magnetometry, magneto-optical Kerr microscopy, and polarized neutron reflectometry to clarify the effects of competing interfacial exchange-bias and lateral interface contributions. Structures of varying ferromagnetic layer thickness and stripe period were analyzed systematically at the frozen-in domain state of oppositely aligned stripe magnetization. For all samples the mean magnetization of the magnetic hybrid structures was found to be aligned nearly orthogonally with respect to the stripe axis and the set exchange-bias direction. Due to the interaction of interfacial coupling, exchange, and magnetostatic energy contributions, the opening angle of neighboring stripe magnetizations increases with decreasing ferromagnetic layer thickness and increasing stripe period. The experimental observations are in agreement with an earlier proposed model for designing micropatterned exchange-bias films.

Structural and magnetic characterization of [Co2MnGe/MgO]n and [Co2MnGe/Al2O3]n multilayers by polarized neutron reflectivity

Magnetic tunnel junctions (MTJ) have become of strategic importance due to the large tunneling magnetoresistance ratio (TMR) that they can achieve at room temperature. The largest TMR values observed until now were recorded in MTJs with MgO barriers and CoFeB electrodes after annealing of the junction above the recrystallization temperature of the amorphous CoFeB layers. We have used x-ray reflectivity combined with polarized neutron reflectivity to characterize the structure and the magnetism of [Co60Fe20B20∕MgO]14 multilayers, where the MgO layers were prepared by different methods and annealed at different temperatures. We have found that the MgO preparation method as well as the annealing temperature play a significant role in the systems. A gradient in thickness together with a variation of the scattering length density along the multilayer stacks induce a process of underoxidation or overoxidation, strictly dependent on the MgO production method.

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

Despite the fact that the magnitude of surface slip, which may occur for a liquid flowing past a solid wall, was quantified by different experimental techniques, the microscopic origin of this effect remains unclear. In the present article we present a neutron reflectivity study for a Newtonian liquid, hexadecane, in contact with solid walls at rest and under shear. In this system slip is not explained by a depleted liquid layer.