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In this study, we report a method to optimize the coercivity keeping the magnetostriction value constant in electrodeposited CoP multilayers for their applications in magnetoelastic magnetic sensors. We have deposited multilayers of two different compositions of CoP (Co0.74P0.26 and Co0.83P0.17) and studied the influence of the thickness of the different layers, keeping the total thickness constant. The results show a saturation magnetostriction in between the values of the magnetostriction of the two materials and independent of the thickness of the layers. However, the reduction of the thickness of the layers is accompanied with a clear reduction of the coercive field to values as low as 0.5 Oe and with a large increase of the permeability. This result shows, in the same material, an appreciable value of magnetostriction combined with low coercivity. Additionally we have found a controllable influence of the hydrogen flow on the direction of anisotropy which, in combination with other results, allows us to customize the material for its application in magnetic sensors. [ABSTRACT FROM AUTHOR]

The transition between Kondo and Coulomb blockade effects in discontinuous double magnetic tunnel junctions is explored as a function of the size of the CoPt magnetic clusters embedded between AlOx mnnel barriers. A gradual competition between cotunneling enhancement of the tunneling magnetoresistance (TMR) and the TMR suppression due to the Kondo effect has been found in these junctions, with both effects having been found to coexist even in the same sample. It is possible to tune between these two states with temperature (at a temperature far below the cluster blocking temperature). In addition, when further decreasing the size of the CoPt clusters, another gradual transition between the Kondo effect and direct tunneling between the electrodes takes place. This second transition shows that the spin-flip processes found in junctions with impurities in the barrier are in fact due to the Kondo effect. A simple theoretical model able to account for these experimental results is proposed. [ABSTRACT FROM AUTHOR]

A new magnetic sensor with a great sensitivity and simplicity is presented. This device is based on the magnetostatic repulsion force between induced magnetic poles. The force of repulsion between a set of two magnetic plates magnetized by an applied field is measured by using one of them as a cantilever. The measurement of the cantilever bending allows to measure the value of the applied magnetic field. An analytical model has been developed to study the best sensor shape. Two experimental methods are proposed: electrical and optical, with different resolution (minimum detectable field of 10 μT and 300 nT, respectively) but both of them with a sensitivity of 10 V/T approximately. [Copyright &y& Elsevier]

In a previous work [Phys. Rev. B 85, 214408 (2012)], the conductance and the tunneling magnetoresistance in discontinuous high anisotropy magnetic tunnel junctions was experimentally studied. Different conduction regimes (sequential tunneling, co-tunneling, Kondo effect, and direct tunneling) and gradual transitions between them were found as a function of the temperature and the size of the clusters within the barrier. A simple theoretical model was suggested able to account for the experimental results even assuming no dispersion of the distribution of the size of the clusters. Here, we study, within this theoretical framework, the effect of the volume of the clusters within the barrier, and the effect of the thickness of the insulating barrier (or the tunnel resistance), on the transition between Kondo effect and co-tunneling regime. Clarifying the role of both parameters is of importance to understand and experimentally control the transition between the different conduction regimes. [ABSTRACT FROM AUTHOR]

In this work, we report the magnetic properties of sputtered Permalloy (Py: Ni80Fe20)/molybdenum (Mo) multilayer thin films. We show that it is possible to maintain a low coercivity and a high permeability in thick sputtered Py films when reducing the out-of-plane component of the anisotropy by inserting thin film spacers of a non-magnetic material like Mo. For these kind of multilayers, we have found coercivities which are close to those for single layer films with no out-of-plane anisotropy. The coercivity is also dependent on the number of layers exhibiting a minimum value when each single Py layer has a thickness close to the transition thickness between Neel and Bloch domain walls. [ABSTRACT FROM AUTHOR]

It is common to find a thin (∼0.5 nm) layer of Mg deposited prior to the MgO tunnel barrier in crystalline CoFe(B)/MgO/CoFe(B) magnetic tunnel junctions, due to the improved device performance that results. However, despite their common usage, the reasons why such layers are effective are unclear. We use structures that model the lower electrode of such devices to show that a suitably thick Mg insert layer enhances the crystal quality of both MgO and CoFe(B), permits interfacial oxides to reduce back to a metallic ferromagnetic state, and hence improves magnetic switching of the CoFe(B) electrode, properties which are inextricably linked to device performance. [ABSTRACT FROM AUTHOR]

The current-induced resonance frequencies of domain walls in parabolic pinning potentials are measured in Gd doped NiFe as a function of doping level. The modification of magnetic properties due to Gd doping results in an order of magnitude increase in resonance frequencies for 10% Gd doping, due to the induced out-of-plane anisotropy, and the resonance frequencies are excited at lower current densities compared to undoped NiFe. These results are reproduced using a one-dimensional model of domain wall resonance, and found to be in good agreement in the small oscillation amplitude limit. [ABSTRACT FROM AUTHOR]

We have studied the effect of annealing on the interface magnetization in a CoFeB/MgO structure which models the lower electrode in a magnetic tunnel junction device. We find that MgO deposition causes Fe to diffuse toward the CoFeB/MgO interface, where it preferentially bonds with oxygen to form a Fe-O-rich interfacial region with reduced magnetization. After annealing at 375 °C the compositional inhomogeneity remains; Fe is reduced back to a ferromagnetic metallic state and the full interfacial magnetization is regained. [ABSTRACT FROM AUTHOR]