Search

First-principle calculations were used to simulate the changes in magnetic parameters and interatomic charge density in the crystal structure of yttrium iron garnet (YIG) caused by Ca–Sn co-doping. The simulation results illustrate that Ca and Sn have no spin polarization in the crystal, and the charge density among ions tends to increase with doping concentration. A solid-state reaction method was employed to prepare YIG with varying concentrations of Ca–Sn co-doping. The saturation magnetization ($4\pi M_{s}$) of the material shows an initial increase and then decrease as the number of doping increases. This phenomenon of increment in $4\pi M_{s}$ at first could be accounted for the increase of the net magnetic moment of material. The reduction in $4\pi M_{s}$ could be interpreted as the content of Fe3+ ($5~\mu \text{B}$) decreases, while the Fe2+ ($4~\mu \text{B}$) in the material becomes the primary portion when the concentration of doping exceeds 0.10. [ABSTRACT FROM AUTHOR]

A mesoscopic multi-terminal superconducting Nb strip with a spin injection terminal has been developed. We investigate the influence of spin polarization on the relaxation process of the quasiparticle in the superconducting Nb. The position dependence of the nonlocal voltage provides the quasiparticle relaxation length. The relaxation length for the spin-polarized quasiparticle is found to show a 12.5% increase from that for the un-polarized quasiparticle. This demonstration opens a new avenue for utilization of the spin current in a superconducting device. [ABSTRACT FROM AUTHOR]

The results of the optical properties study and the electronic structure calculation of ${\text{Co}}_{2}Y\text {Si}$ ($Y = \text {Ti}$ , V, Cr, Mn, Fe) Heusler alloys are presented. Temperature dependences of the electrical resistivity were studied in the temperature range from 4.2 to 300 K. Field dependences of magnetization were measured in the magnetic fields of up to 5 T. The main attention is paid to the spectral dependence of the real and imaginary parts of the dielectric constant in the wavelength range from 0.3 to $8~\mu \text{m}$ by the ellipsometric Beattie method at room temperature. Anomalous behavior of optical conductivity at infrared (IR) frequencies in Co2TiSi and Co2VSi alloys was found, which significantly differs from that in Co2MnSi, Co2FeSi, and Co2CrSi. The results obtained are discussed based on calculations of the electronic structure. Simultaneously, the correlations between the changes in these characteristics can be an indicator of the states of a half-metallic ferromagnet (HMF) or a spin gapless semiconductor (SGS). A high degree of charge carriers’ spin polarization is possible in such materials, and therefore, they are promising materials for spintronics. [ABSTRACT FROM AUTHOR]

We theoretically investigate the dwell time for electrons in an antiparallel double δ-magnetic-barrier nanostructure, which is constructed on the surface of the InAs/AlxIn1-xAs heterostructure by patterning two ferromagnetic (FM) stripes. It is shown that the dwell time is dependent on electron spins due to the spin–field interaction between spins and magnetic fields. It is also shown that both magnitude and sign of the spin polarization in the dwell time can be modulated by the structural width or magnetic-strength difference between two magnetic barriers, which may give rise to a controllable temporal spin splitter for spintronics device applications. [ABSTRACT FROM AUTHOR]

We report on the successful spin injection from EuS/Co multilayers into (100) GaAs at low temperatures. The spin injection was verified by means of polarized electroluminescence (EL) emitted from AlGaAs/GaAs-based spin-light-emitting diodes in zero external magnetic field. Spin-polarized electrons were injected from prototype EuS/Co spin injector multilayers. The use of semiconducting and ferromagnetic EuS circumvents the impedance mismatch. The EL was measured in side emission with and without an external magnetic field. A circular polarization of 5% at 8 K and 0 T was observed. In view of the rather rough interface between the GaAs substrate and first EuS layer, improvement of the interface quality is expected to considerably enhance the injected electron spin polarization. [ABSTRACT FROM AUTHOR]

The 1-D nanoscale structures are studied with a potential relief containing magnetic barriers separated by nonmagnetic quantum wells in the absence of exchange interaction between the magnetic moments of adjacent barriers. The considered structure is the sequence of N barriers divided into two “ferromagnetic domains” of the length n and N - n -- 1, both having parallel internal fields. In contrast, the internal field of the nth barrier is not coplanar with respect to the internal fields of the left and/or right “domains.” The degree of spin polarization of an electron wave transmitted through this system is calculated with the assumption that the incident wave is unpolarized with the degree of its polarization equals zero. It is shown that the degree of polarization of the transmitted wave as a function of the impulse exhibits a sequence of sufficiently wide plateaus, which are close to unity. In particular, there are significant deviations from the known spintronics phenomena found earlier in this system such as the valve, filter, and giant magnetoresistance effects. This circumstance provides opportunities for managing the transport properties of the system by varying the noncoplanar degrees of freedom of the system. [ABSTRACT FROM AUTHOR]

We show that there is a crystal orientation effect on the two-terminal local magnetoresistance (MR) in silicon (Si)-based lateral spin-valve (LSV) devices. When we compare the local MR effect between Si $\langle 100\rangle $ and Si $\langle 110\rangle $ LSV devices, the magnitude of the local MR signals for Si $\langle 100\rangle $ LSV devices is always larger than that for Si $\langle 110\rangle $ LSV devices. For Si $\langle 100\rangle $ LSV devices, the magnitude of the room-temperature MR ratio reaches approximately 0.06%. We infer that it is important to consider the tunneling anisotropic spin polarization, which is due to the magnetization direction of the ferromagnetic contacts relative to the Si crystal orientation, in the fabricated LSV devices. [ABSTRACT FROM AUTHOR]

Structural, electronic and magnetic properties of the Heusler alloy Mn2VIn have been investigated using the density functional theory and experimental techniques. Unlike many other Heusler compounds, Mn2VIn is not predicted to be half-metallic at the optimized lattice constant, but is highly spin polarized at a slightly lower lattice constant. It however exhibits ferrimagnetic coupling between the Mn and V sublattices, as expected of Mn-based Heuslers. We have, then, synthesized the compound by arc melting and studied magnetic properties that are of interest fundamentally and for technological applications. The structural properties were determined using X-ray diffraction, revealing the presence of cubic and tetragonal phases in the sample. The chemical composition was determined using energy-dispersive X-ray spectroscopy together with the scanning electron microscope, and the magnetic properties were investigated by superconducting quantum interference device magnetometry. The alloy exhibits superparamagnetic spin blocking with a blocking temperature TB of 40 K. [ABSTRACT FROM AUTHOR]

In this paper, we propose the use of magnetic skyrmion sensors for low-voltage, low-current global interconnects. Magnetic skyrmions have shown great potential for low-power circuit applications, since skyrmions can be generated and moved by remarkably low-current pulses. We propose the use of skyrmion-based current sensors at the receiver that allows low-current signal transmission through the line. The proposed skyrmion sensor consists of a magnetic nanotrack on top of a spin-Hall metal (SHM). The skyrmion is nucleated in the nanotrack by using spin-polarized current and, subsequently, moved along the nanotrack by using a charge current through the SHM. This charge current is the input current from a global interconnect line, which moves the skyrmion depending on the logic input to the line. The resistance of a magnetic tunnel junction (MTJ) at the receiver is based on the movement/location of the skyrmion. This resistance change is sensed using a reference MTJ and a simple complementary metal–oxide–semiconductor (CMOS) inverter. Such a receiver configuration acts as a built-in latch, and hence, expensive voltage converters or transimpedance amplifiers can be avoided, which are the bottlenecks in a conventional low-power interconnect design. Our simulation results indicate that for a 10 mm Cu-line in 45 nm CMOS technology, the energy consumption with skyrmion-based sensing is $\sim 50\times $ lower compared with full swing and $\sim 25\times $ lower compared with low-swing CMOS interconnect. [ABSTRACT FROM AUTHOR]

In this paper, we propose a Pt-doping method to effectively decrease the phase transformation temperature of Co2FeAl0.5Si0.5 (CFAS) from A2 phase to B2 phase based on first-principle calculations. It has been demonstrated that the Pt atom tends to reside in the Si site to lower the system free energy. Meanwhile, the spin polarization can be reserved as 100% after Pt doping in a proper concentration less than 3.125%. Transition state search shows that the atomic diffusion barrier of Pt-doped CFAS is lower than that of the CFAS. Therefore, Pt doping in CFAS is a possible method to obtain ordered B2 phase at low annealing temperature. [ABSTRACT FROM AUTHOR]

We theoretically investigate the effect of stray field on the current-induced magnetization dynamics in a nanopillar with a perpendicular spin polarizer. The threshold current to excite out-of-plane (OP) magnetization procession is analytically calculated based on a simple Newton-like dynamic equation. The numerical calculations of this analytical expression are confirmed by macrospin simulations, revealing that the critical current linearly depends on the stray field. The stray field versus current phase diagram of magnetization oscillation states in such a device is presented, showing three regions of magnetization dynamics including parallel, antiparallel, and OP precession states. The physical insight of the phase transitions between the three states can be explained by calculating the energy profiles as well as the phase portraits of the free layer. [ABSTRACT FROM AUTHOR]

Motion of the magnetic domain walls under the pulses of magnetic field or spin-polarized electric current is studied experimentally by direct visualization of the walls. The experiments are performed in the temperature range from 300 down to 6 K. Coercivity, mobility of the walls, and their variations with temperature are investigated. Wall velocity is observed to increase by orders of magnitude due to cooling from room to helium temperature in the case of current stimulated motion. The velocity becomes as high as the Walker velocity limit, about 1000 m/s. The walls are found to expand and tilt under the current pulses, which leads to their transformation into the domains with transverse magnetization. [ABSTRACT FROM AUTHOR]

An important step has been developed combining the potential of spintronics with organic electronics to reveal the promising field of molecular spintronics, which can offer more flexibility, higher recyclability, and low-production costs compared with inorganic devices. Room temperature magnetoresistance (MR) of 5% has been obtained from C60 spin valves with the structure Co(20 nm)/Al2 O3(1.2 nm)/C60 (5–60 nm)/Py(20 nm)/Al(1.5 nm). We observe an asymmetric dependence at low temperatures of the MR with voltage, and surprisingly with the magnetic field as well. This behavior has been attributed to the organic interface formed at the junction, which results in a change of the ferromagnet’s spin polarization. The spin polarization at the organic-ferromagnetic interface is extracted by measuring the bias dependence of the conductance of a metallic-superconducting point contact and analyzed the spectra with the modified Blonder–Tinkham–Klapwijk theory. Point-contact Andreev reflection measurements reveal that the Co–C60 possess spin polarization of 30% ± 1%, compared with 40% ± 1% for our Co films without C60. This could account for the asymmetry of the MR in spin valves incorporating C60 and the need for an alumina spacer to maximize the MR. [ABSTRACT FROM AUTHOR]

The persistent spin helix (PSH) occurs in 2-D nanosystems where the Rashba and Dresselhaus spin orbit interactions (RSOI/DSOI) are both present and of equal strength. The spin orbit interaction effective field experienced by the charge carriers due to RSOI and/or DSOI generally depends on the direction of the charge carrier momenta. The PSH is unique in that the direction of this effective magnetic field is independent of the momentum direction. We find that this results in the spin accumulation in a PSH system assuming only the PSH eigenspinor directions of ±(1, −1, 0) without any intermediate directions in between, when spin unpolarized electrons are injected into the PSH system. This can be explained by the accumulation of the spin up and spin down carriers about the PSH eigenspinor axis occurring in opposite directions, resulting in the the spin components perpendicular to ±(1, −1, 0) averaging to zero. In particular, the spin accumulation for an infinitely wide PSH segment connected to a narrow spin unpolarized source lead is partitioned between the (1, −1, 0) and (−1, 1, 0) directions along the upper and lower halves of the segment about the source lead-PSH interface. This partitioning of the spin accumulation motivates the proposal of a finite-sized PSH spin polarizer for generating ±(1, −1, 0) spin polarized currents. The spin polarization of the current can be optimized by reducing the length and increasing the width of the spin polarizer. [ABSTRACT FROM AUTHOR]

An alloy of Fe35 Al50 B15 has been prepared by milling under vacuum for 840 h. The X-ray diffraction pattern shows only two broad peaks stemming from a highly disordered structural state. The magnetic state was characterized by AC susceptibility. It displays sharp maxima around 20 K (21 K) in the real (complex) components. The maxima are due to the onset of a spin frozen disordered arrangement, and shift to higher temperature with increasing frequency. The magnetic dynamics is accounted for a power-law in the vicinity of the transition. Values of z \(\upsilon = 9.0\) (3) and T0 = 19.5 (1) K are obtained. Complex susceptibility dynamic scaling results in a large \(\beta = 1.3\) (1). The values extracted for the critical exponents are close to those of glassy magnets and are an indication of a nonconventional transition. The nonlinear susceptibility reveals a peak at the transition, which is affected by the oscillating \(h < 5\) Oe and biasing ( \(H_{\mathrm {\mathbf {DC}}}\le 40\) Oe) fields. The results are interpreted in terms of the freezing of very fine Fe-rich magnetic particles which are present as the result of an incomplete compositional homogenization despite the long milling time. [ABSTRACT FROM AUTHOR]

We investigated spin signals for Co2Fe(Al,Si)/n-GaAs Shottoky tunnel junctions by three terminal (3T) Hanle and four terminal (4T) non-local measurements. The ordering structure and magnetic moment increased with \(T_{\mathrm {\mathbf {CFAS}}}\) up to 300 °C. The spin signals for Co2Fe(Al,Si)/n-GaAs Shottky tunnel junctions were clearly observed and these were also affected by \(T_{\mathrm {\mathbf {CFAS}}}\) , however, the T \(_{\mathrm {\mathbf {CFAS}}}\) dependency was different obtained from 3T Hanle and 4T non-local measurements. The spin signals in 3T Hanle measurement decreases with increasing \(T_{\mathrm {\mathbf {CFAS}}}\) up to 300 °C and increase for the sample with \(T_{\mathrm {CFAS }}= 400\) °C. On the other hand, the spin signals in 4T non-local measurement increases with \(T_{\mathrm {\mathbf {CFAS}}}\) up to 300 °C and decreases for the sample with \(T_{\mathrm {CFAS }}= 400\) °C. This result obtained from 4T non-local measurement could be explained by the spin polarization of Co2Fe(Al,Si), and that from 3T Hanle measurement would not come from the spin polarization of Co2Fe(Al,Si) but other source, such as localized state around the interface between Co2Fe(Al,Si) and n-GaAs. [ABSTRACT FROM AUTHOR]

An Si spin interconnect for all-spin logic (ASL) is analyzed by a comprehensive physical model, including spin injection, spin transport, and stochastic magnetization dynamics. It is shown that the spin current density and spin polarization of the current can be improved by changing material properties, interface conditions, and structure dimensions. Furthermore, with the help of an electric field, spin information can preserve and propagate between magnets in a highly doped micrometer-scale Si channel. Different from metallic ASL, instead of the short spin relaxation length, the main constraint of an Si spin interconnect is the high bias voltage required to minimize the energy-delay product (EDP). The minimum EDP and corresponding bias voltage can be reduced significantly by downscaling the nanomagnet. This improvement in the magnetic response allows Si to provide a compatible low-power interconnect technology to metallic ASL. [ABSTRACT FROM AUTHOR]

We report spin polarization P of Fe-rich Heusler alloy \Ru0.2{\Fe}1.8{\CrSi}, which was determined by the Andreev reflection technique. Heusler alloy \Ru2-x{\Fe}_x{\CrSi} was predicted to be half-metal by the first-principle band calculations. Fe-rich \Ru0.2{\Fe}1.8{\CrSi} compounds are ferromagnetic and the saturation magnetization M_0 almost coincides with that expected from the Slater-Pauling rule. Two theoretical approaches in the determination of spin polarization by Andreev reflection are discussed and compared from an experimental perspective. The spin polarization more than P=0.60 is obtained for \Ru0.2{\Fe}1.8{\CrSi} specimens and it is highest value in all \Ru2-x{\Fe}_x{\CrSi} compounds. The difference in values of spin polarization as determined by two models is less than 0.02. [ABSTRACT FROM AUTHOR]

This work presents an experimental study of the magnetotransport properties in the Heusler compound \Pd2{\MnSn}. The electrical resistivity, magnetoresistance and Hall effect were measured in the temperature interval between 2 K and 350 K in the presence of magnetic fields ranging between 0 and 9 Tesla. Magnetization measurements were made as a complement to the magnetotransport experiments. Effects of spin polarized electronic currents were evidenced in the magnetotransport experiments. In particular, the spin mixing term that describes the momentum transfer between the spin dependent subbands, plays an important role in the low temperature resistivity and magnetoresistance. On the other hand, the scattering processes due to spin disorder are dominant in the intermediate and high temperatures regions. The temperature dependent Hall resistivity in \Pd2{\MnSn} shows a minimum around T=50\ \K. An anomalous contribution to the Hall effect in this system was identified and discussed with basis on the k-space Berry phase theoretical predictions. [ABSTRACT FROM AUTHOR]

This article reports a comparative study of the spin pumping induced by graphite and graphene layers adjacent to an extended ferromagnetic Permalloy film. The corresponding enhancement of the Gilbert damping in the ferromagnet is determined by analyzing the frequency dependence of the ferromagnetic resonance linewidth in experiments done with a broad band microwave spectrometer. The results show that a single graphene layer is more efficient than a thick graphite film in absorbing the angular momentum pumped away from the Permalloy during the resonant precession of its magnetization. We associate this effect to an enhancement of the spin-orbit coupling in the graphene layer due to Copper adatoms residual from the chemical vapor deposition process used to synthesize the graphene used in the experiments. [ABSTRACT FROM AUTHOR]

The spin Coulomb drag is a distinctive feature of spin-polarized transport. The current of majority spins can induce a current of minority spin carriers via the transconductivity. The friction is caused by the Coulomb interaction between up- and down-spin. This interaction reduces the current but does not change the spin-polarization. We calculate the conductivities and the transconductivity for a spin-polarized interacting 1-D electron gas for a lattice without inversion symmetry in the presence of nonmagnetic impurities. Due to the Luttinger liquid properties, the temperature dependence of the transport correlation functions follows power laws of with nonuniversal exponents. [ABSTRACT FROM AUTHOR]

To examine the influence of the barrier quality in fully epitaxial Fe/MgO/Fe(001) magnetic tunnel junctions (MTJs), we propose to use Fe-V alloys as magnetic electrodes. This leads to a reduced misfit with MgO. We actually observe, by high-resolution electron microscopy (HREM) and local strain measurements, that the misfit dislocations density in the MgO barrier is lower when it is grown on Fe-V(001). This improvement of the crystalline quality of the MgO barrier actually leads to a significant increase of the tunnel magneto-resistance (TMR), despite the loss of spin polarization (SP) in these alloys, which was measured by spin-polarized X-ray photoelectron spectroscopy (SR-XPS). [ABSTRACT FROM AUTHOR]

The unique properties of synchrotron radiation, such as broad energy spectrum, variable light polarization, and flexible time structure, have made it an enormously powerful tool in the study of magnetic phenomena and materials. The refinement of experimental techniques has led to many new research opportunities, keeping up with the challenges put up by modern magnetism research. In this contribution, we review some of the recent developments in the application of synchrotron radiation and particularly soft X-rays to current problems in magnetism, and we discuss future perspectives. [ABSTRACT FROM AUTHOR]

We investigate spin-dependent bandgap structures and spin filtering in graphene with multiple ferromagnetic barriers. Using the transfer matrix method, we have calculated the spin-dependent transmission coefficients, the spin polarization, the conductance, and the electronic energy spectra of the systems. It is shown that the spinup and spindown electrons possess different bandgap structures. As a result, full spin polarization can be achieved within several separated energy zones. The width of the energy zone with full spin polarization can be effectively manipulated by adjusting the exchange field. Correspondingly, conductance steps with full spin polarization are observed in the systems. Our investigations may have potential applications in the design of carbon-based spin filters. [ABSTRACT FROM AUTHOR]

We present a theoretical study of spin ploarized transport in a single-electron tunneling transistor with ferromagnetic source and drain electrodes. The sequential tunneling and cotunneling currents are analyzed as a function of the intrinsic spin polarization of the electrodes, and spin flip effects within the central island electrode, for the case of collinear magnetization configuration. It was found that an antiparallel alignment of the electrode magnetization leads to a suppression of both the sequential tunneling and cotunneling currents, with the degree of suppression being greater for the higher order cotunneling current. For the sequential case, the suppression can be reduced by introducing finite spin flip within the island, but this has virtually no effect on the cotunneling current. [ABSTRACT FROM AUTHOR]

Interlayer exchange coupling (IEC) behavior in epitaxial Co[sub2] MnSi (20 nm)/CrIFe (7 nm) trilayers has been investigated against Cr spacer thickness (t[subCr] = 0.3-6.3 nm). High-quality trilayer samples have grown on a Cr (5 nm)/Au (30 nm)/Cr (15 nm) buffer layer on a MgO substrate by ultrahigh vacuum (UHV) compatible dc sputtering method. A simple numerical simulation model has been used to explain magnetization process, which shows good agreement with the experimental M - H curves. The values of bilinear and biquadratic coupling energy (J[sub1] and J[sub2]) and the cubic anisotropy energy of Co[sub2] MnSi and Fe (K[subCMS] and K[subFe]) have been determined uniquely from the simulations. As a result, we have found a dominating contribution of biquadratic (90°) coupling and absence of bilinear (180°) coupling in all the samples with nonferromagnetic coupling. It has also been found that, the energetical competition between 90° coupling energy and anisotropy energy largely affects the magnetization process due to different easy directions of bottom Co[sub2] MnSi (110) and Fe (100). [ABSTRACT FROM AUTHOR]

We present a heat-treatment-free fabrication technique for pseudo current-perpendicular-to-plane giant magnetoresistance (CPP-GMR) structures with a highly spin-polarized Co-based Heusler-compound electrode. Room-temperature molecular beam epitaxy enables an all-epitaxial Heusler compound/metallic spacer/Heusler compound, i.e., Fe3Si/FeSi/Co2FeSi, trilayer structure. Since each layer includes ideally ordered structures, the magnetization reversal process of the trilayer is changed from two-step switching to one-step switching upon cooling through the paramagnetic–ferromagnetic transition of the ordered FeSi spacer layer. This paper will open a way for high-performance CPP-GMR devices with Co-based Heusler compounds. [ABSTRACT FROM AUTHOR]

We have investigated electronic and magnetic properties of a (110) film of half-metallic Heusler \Fe2{\CrSi} by the first-principle band calculations and have found that the (110) film is not half-metallic but has a high spin polarization (P = 82\%). The result for \Fe2{\CrSi}/\Fe2{\VAl} interface shows that the spin polarization is improved up to 96%. Our present results for (110) film, as well as the previous ones for (001) and (111) films, shows that it is possible to obtain a high spin polarized film by making a choice of a suitable surface for each one of (001), (110), and (111) films. [ABSTRACT FROM AUTHOR]

The spin polarization at the surface of Fe nanoclusters has been probed using a spin-polarized metastable helium beam. The clusters, produced in a gas aggregation source, display a lognormal size distribution with a peak centered at ~11 nm. Varying coverages of both spheroid- and cuboid-shaped particles were concomitantly deposited onto clean Si(111) substrates for investigation with the extremely surface sensitive technique of metastable de-excitation spectroscopy (MDS). A nominal cluster coverage of 8 Å yielded a maximum asymmetry of ~10% in the ejected electron yield for He spins aligned parallel and anti-parallel to the magnetization direction of the clusters. When compared to values obtained from epitaxial Fe films on various substrates, the measured asymmetry suggests an enhancement in the surface spin polarization, as theoretically proposed. The atomic structure of the clusters and their topography on the Si(111) substrates were studied with transmission and scanning electron microscopy. [ABSTRACT FROM AUTHOR]

Thin films of Ni80Fe20, Fe3O4, as well as Ni80Fe20/Cr/Fe3O4 spin valves, have been grown with and without magnetic fields applied during the deposition, and their magnetotransport properties have been studied at room temperature. The applied field induces an anisotropy in both single layer films, which causes notable differences in their anisotropic magnetoresistance. In the spin valve system, the applied field enables the parallel and antiparallel states to be more well-defined, which reveals a possible giant magnetoresistance in the system. The origin of this signal is likely the interaction of electrons that have been polarized by spin-dependent reflection from the Cr/Fe3O4 interface with the Ni80Fe20 interface. [ABSTRACT FROM AUTHOR]

In this paper, variation in magnetoresistance (MR) by transition-metal (TM) doping in magnetite (Fe3O4) has been investigated. The samples(TxFe3-xO4, T = V, and Cr) were polycrystalline and prepared as thin films by a sol-gel method. As the TM composition (x) increases, the MR strength is reduced but the reduction rate with x differs significantly for the two TM-doping cases. For the V-substituted samples, the MR is reduced rapidly with x and no significant MR is detected above x = 0.11. On the other hand, the Cr-substituted samples exhibit the MR effect up to x = 0.49. Such difference in MR strength between the two TM-doping cases is attributable to the difference in the intrinsic properties of the ternary ferrites such as electronic structure and carrier spin polarization. [ABSTRACT FROM AUTHOR]

We have obtained high-quality tunnel junctions with MgO barriers and superconducting Al bottom electrodes by sputter deposition and plasma oxidation. These junctions were used for spin-polarized tunneling measurements in which the Zeemanisplit superconducting density of states is used to determine directly the tunneling spin polarization with Co and Fe top electrodes. Similar attempts with Ta2 O5 barriers resulted in poor quality of the superconducting gap, with drastically reduced width, for both Al and V superconducting bottom electrodes. [ABSTRACT FROM AUTHOR]