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We analyze coexistence of antiferromagnetic and ferromagnetic phases in bulk iron-rhodium and its alloys with palladium, Fe50,4Rh49,6, Fe49,7Rh47,4Pd2,9 and Fe48,3Rh46,8Pd4,9, using neutron diffraction, magnetization and scanning Hall probe imaging. Temperature dependencies of the lattice parameters, AFM and FM phase weight fractions, and Fe magnetic moment values were obtained on cooling and heating across the AFM-FM transition. Substantial thermomagnetic hysteresis for the phases’ weight fractions and a relatively narrow one for the unit cell volume has been observed on cooling-heating. A clear dependence of hysteretic behavior on Pd concentration has been traced. Additional direct magnetic measurements of the spatial distribution of the phase transition are acquired using scanning Hall probe microscopy, which reveals the length scale of the phase coexistence and the spatial progression of the transition in the presence of external magnetic field. Also, the magnetic phase diagram has been constructed for a series of Pd-doped FeRh alloys. © 2020 Elsevier B.V.

We report the room temperature operation of a quasi-ballistic InSb quantum well Hall sensor that exhibits a high frequency sensitivity of 560nT/root Hz at 20uA bias current. The device utilizes a partitioned buffer layer design that suppresses leakage currents through the mesa floor and can sustain large current densities.

We report the room temperature operation of a quasi-ballistic InSb quantum well Hall sensor that exhibits a high frequency sensitivity of 560nT/root Hz at 20uA bias current. The device utilizes a partitioned buffer layer design that suppresses leakage currents through the mesa floor and can sustain large current densities.

We report the low temperature magnetoresistance properties of an InSb quantum well sub-micron Hall cross with lateral dimensions of 477 nm and active device dimensions of the order of 340 nm. Ballistic transport anomalies are observed in the low field regime including negative bend resistance. The use of such devices as high spatial resolution low field sensors is addressed.

We report the room temperature observation of significant ballistic electron transport in shallow etched four-terminal mesoscopic devices fabricated on an InSb/AlInSb quantum well (QW) heterostructure with a crucial partitioned growth-buffer scheme. Ballistic electron transport is evidenced by a negative bend resistance signature which is quite clearly observed at 295 K and at current densities in excess of 10(6)A/cm(2). This demonstrates unequivocally that by using effective growth and processing strategies, room temperature ballistic effects can be exploited in InSb/AlInSb QWs at practical device dimensions.

We describe the influence of hard-wall confinement and lateral dimension on the low-temperature transport properties of long diffusive channels and ballistic crosses fabricated in an InSb/In1-xAlxSb heterostructure. Partially diffuse boundary scattering is found to play a crucial role in the electron dynamics of ballistic crosses and substantially enhance the negative bend resistance. Experimental observations are supported by simulations using a classical billiard ball model for which good agreement is found when diffuse boundary scattering is included.

We report the low temperature magnetoresistance properties of an InSb quantum well sub-micron Hall cross with lateral dimensions of 477 nm and active device dimensions of the order of 340 nm. Ballistic transport anomalies are observed in the low field regime including negative bend resistance. The use of such devices as high spatial resolution low field sensors is addressed.

We report the room temperature observation of significant ballistic electron transport in shallow etched four-terminal mesoscopic devices fabricated on an InSb/AlInSb quantum well (QW) heterostructure with a crucial partitioned growth-buffer scheme. Ballistic electron transport is evidenced by a negative bend resistance signature which is quite clearly observed at 295 K and at current densities in excess of 10(6)A/cm(2). This demonstrates unequivocally that by using effective growth and processing strategies, room temperature ballistic effects can be exploited in InSb/AlInSb QWs at practical device dimensions.

We describe the influence of hard-wall confinement and lateral dimension on the low-temperature transport properties of long diffusive channels and ballistic crosses fabricated in an InSb/In1-xAlxSb heterostructure. Partially diffuse boundary scattering is found to play a crucial role in the electron dynamics of ballistic crosses and substantially enhance the negative bend resistance. Experimental observations are supported by simulations using a classical billiard ball model for which good agreement is found when diffuse boundary scattering is included.

For Andreev spectroscopy to be a useful tool to detect spin accumulation in semiconductors, we show by simulation that there is a maximum value for the interface scattering parameter that can be tolerated. Three different fabrication routes for Pb/InAs planar junctions are explored and we find that the "etch-back" processing strategy is the most promising. Using the parameters extracted from the spectroscopic analysis, we find that the interface properties fall into four different regimes of behavior. (C) 2008 American Institute of Physics.

The di®usivity ratio ´, which measures the relative intraband scattering in the ¼ and ¾ bands in MgB2 has been determined by ¯tting the Hc2(T) at T » Tc and by Point Contact Andreev Re°ection. We ¯nd a satisfactory agreement between the values for ´ obtained by both methods for c-axis orientated MgB2 thin ¯lms. Point contact Andreev Re°ection was then applied to bulk MgB2 containing Mg vacancies. Spectra obtained in zero ¯eld indicate a distribution of the two gaps ¢¾;¼ but no merging of the values with increased magnesium de¯ciency. Spectra ¯tted as a function of ¯eld are consistent with an increase in ¼ intraband scattering with increasing magnesium de¯ciency. Measurement of the point contact Andreev re°ection spectra as a function of temperature revealed features not immediately expected from current theoretical models.

The di®usivity ratio ´, which measures the relative intraband scattering in the ¼ and ¾ bands in MgB2 has been determined by ¯tting the Hc2(T) at T » Tc and by Point Contact Andreev Re°ection. We ¯nd a satisfactory agreement between the values for ´ obtained by both methods for c-axis orientated MgB2 thin ¯lms. Point contact Andreev Re°ection was then applied to bulk MgB2 containing Mg vacancies. Spectra obtained in zero ¯eld indicate a distribution of the two gaps ¢¾;¼ but no merging of the values with increased magnesium de¯ciency. Spectra ¯tted as a function of ¯eld are consistent with an increase in ¼ intraband scattering with increasing magnesium de¯ciency. Measurement of the point contact Andreev re°ection spectra as a function of temperature revealed features not immediately expected from current theoretical models.

For Andreev spectroscopy to be a useful tool to detect spin accumulation in semiconductors, we show by simulation that there is a maximum value for the interface scattering parameter that can be tolerated. Three different fabrication routes for Pb/InAs planar junctions are explored and we find that the "etch-back" processing strategy is the most promising. Using the parameters extracted from the spectroscopic analysis, we find that the interface properties fall into four different regimes of behavior. (C) 2008 American Institute of Physics.

In order to introduce structural defects into the band with minimal distortions in the band, bulk samples of varying magnesium content were prepared. Point contact Andreev reflection measurements reveal that the density of states of the band and the behavior of the energy gaps in field imply a relative increase of band to band scattering with increasing magnesium deficiency. The results are consistent with the observed increase of the low temperature Hc2 value in magnesium deficient MgB2.

In this study we compare the critical current density, the irreversibility line and the upper critical field of four MgB2 polycrystalline samples, which are either undoped or have 5% carbon or 5% carbon plus either 1% aluminium or 2% zirconium. We discuss how care must be taken for the extraction of the irreversibility line in such samples. We also show how ac susceptibility and Hall probe imaging can be used to examine whether the samples remain fully connected to the highest available fields. Compared to simple 5% carbon doping we find that co-doping provides modest improvement in the pinning properties at intermediate fields in the carbon plus zirconium doped sample.

The inherent large spin-orbit (SO) coupling InSb quantum wells (QWs) is expected to result in sensitive tunability of the Rashba effect with electric field. The strength of the SO coupling can be extracted from measurements of weak anti-localisation (WAL) and from the beating of Shubnikov-de Haas (SdH) oscillations [1]. We have investigated these phenomena and report magneto transport measurements from a range of InSb/InAlSb QWs with varying carrier density n and mobility μ. It is shown that the inherent large Zeeman splitting combined with inhomogeneous level broadening means that beating in the SdH oscillations in InSb QWs are rarely observed. However, her we show that in InSb/InAlSb QWs, n can be modulated using a gate electric field from 1.15

We report the low temperature magnetoresistance properties of an InSb quantum well sub‐micron Hall cross with lateral dimensions of 477 nm and active device dimensions of the order of 340 nm. Ballistic transport anomalies are observed in the low field regime including negative bend resistance. The use of such devices as high spatial resolution low field sensors is addressed.

The structural integrity, composition and interface quality of tunnel barriers in hybrid ferromagnet-semiconductor structures will have a significant effect on the properties of spintronic devices. We present the results of a study of an amorphous MgO tunnel barrier in a Co/MgO/InAs multilayer structure. Optimum growth parameters for MgO and surface treatment of InAs have been identified by a systematic electron microscopy investigation. Electron energy loss spectroscopy has been used to obtain information on composition and interface quality in the multilayer structures.

A high mobility single subband occupancy InSb/InAlSb quantum well was grown by molecular beam epitaxy. The low-temperature, high-field magnetotransport properties are measured as a function of gate bias. Spin-resolved Shubnikov-de Haas oscillations are observed. A preliminary analysis of the Shubnikov-de Haas oscillations indicates a strong gate bias dependence of the Rashba spin-orbit term.