Search

We present detailed experimental measurements and simulations of the field-dependent magnetization and magnetoresistance in the vicinity of the Curie temperature in the highly disordered dilute ferromagnetic semiconductor (Ga,Mn)As. The observed dependence of the magnetization on external magnetic field and temperature is consistent with three-dimensional Heisenberg equation of state calculations including a narrow distribution of critical temperatures. The magnetoresistance shows a peak at the Curie temperature due to the suppression of magnetic scattering in an applied magnetic field, which is well-described by considering changes in the square of the magnetization induced by the magnetic field.

Antiferromagnets have several favourable properties as active elements in spintronic devices, including ultra-fast dynamics, zero stray fields and insensitivity to external magnetic fields 1 . Tetragonal CuMnAs is a testbed system in which the antiferromagnetic order parameter can be switched reversibly at ambient conditions using electrical currents 2 . In previous experiments, orthogonal in-plane current pulses were used to induce 90° rotations of antiferromagnetic domains and demonstrate the operation of all-electrical memory bits in a multi-terminal geometry 3 . Here, we demonstrate that antiferromagnetic domain walls can be manipulated to realize stable and reproducible domain changes using only two electrical contacts. This is achieved by using the polarity of the current to switch the sign of the current-induced effective field acting on the antiferromagnetic sublattices. The resulting reversible domain and domain wall reconfigurations are imaged using X-ray magnetic linear dichroism microscopy, and can also be detected electrically. Switching by domain-wall motion can occur at much lower current densities than those needed for coherent domain switching.

Using x-ray magnetic circular and linear dichroism techniques, we demonstrate a collinear exchange coupling between an epitaxial antiferromagnet, tetragonal CuMnAs, and an Fe surface layer. A small uncompensated Mn magnetic moment is observed which is antiparallel to the Fe magnetization. The staggered magnetization of the 5 nm thick CuMnAs layer is rotatable under small magnetic fields, due to the interlayer exchange coupling. This allows us to obtain the x-ray magnetic linear dichroism spectra for different crystalline orientations of CuMnAs in the (001) plane. This is a key parameter for enabling the understanding of domain structures in CuMnAs imaged using x-ray magnetic linear dichroism microscopy techniques.

Concepts for information storage and logical processing based on magnetic domain walls have great potential for implementation in future information and communications technologies. To date, the need to apply power hungry magnetic fields or heat dissipating spin polarized currents to manipulate magnetic domain walls has limited the development of such technologies. The possibility of controlling magnetic domain walls using voltages offers an energy efficient route to overcome these limitations. Here we show that a voltage-induced uniaxial strain induces reversible deterministic switching of the chirality of a magnetic vortex wall. We discuss how this functionality will be applicable to schemes for information storage and logical processing, making a significant step towards the practical implementation of magnetic domain walls in energy efficient computing.

Antiferromagnets offer a unique combination of properties including the radiation and magnetic field hardness, the absence of stray magnetic fields, and the spin-dynamics frequency scale in terahertz. Recent experiments have demonstrated that relativistic spin-orbit torques can provide the means for an efficient electric control of antiferromagnetic moments. Here we show that elementary-shape memory cells fabricated from a single-layer antiferromagnet CuMnAs deposited on a III-V or Si substrate have deterministic multi-level switching characteristics. They allow for counting and recording thousands of input pulses and responding to pulses of lengths downscaled to hundreds of picoseconds. To demonstrate the compatibility with common microelectronic circuitry, we implemented the antiferromagnetic bit cell in a standard printed circuit board managed and powered at ambient conditions by a computer via a USB interface. Our results open a path towards specialized embedded memory-logic applications and ultra-fast components based on antiferromagnets.

Domain wall motion driven by ultra-short laser pulses is a pre-requisite for envisaged low-power spintronics combining storage of information in magnetoelectronic devices with high speed and long distance transmission of information encoded in circularly polarized light. Here we demonstrate the conversion of the circular polarization of incident femtosecond laser pulses into inertial displacement of a domain wall in a ferromagnetic semiconductor. In our study, we combine electrical measurements and magneto-optical imaging of the domain wall displacement with micromagnetic simulations. The optical spin-transfer torque acts over a picosecond recombination time of the spin-polarized photo-carriers that only leads to a deformation of the initial domain wall structure. We show that subsequent depinning and micrometre-distance displacement without an applied magnetic field or any other external stimuli can only occur due to the inertia of the domain wall.

We investigate the role of lithographically-induced strain relaxation in a micron-scaled device fabricated from epitaxial thin films of the magnetostrictive alloy Fe 81 Ga 19 . The strain relaxation due to lithographic patterning induces a magnetic anisotropy that competes with the magnetocrystalline and shape induced anisotropies to play a crucial role in stabilising a flux-closing domain pattern. We use magnetic imaging, micromagnetic calculations and linear elastic modelling to investigate a region close to the edges of an etched structure. This highly-strained edge region has a significant influence on the magnetic domain configuration due to an induced magnetic anisotropy resulting from the inverse magnetostriction effect. We investigate the competition between the strain-induced and shape-induced anisotropy energies, and the resultant stable domain configurations, as the width of the bar is reduced to the nanoscale range. Understanding this behaviour will be important when designing hybrid magneto-electric spintronic devices based on highly magnetostrictive materials., Competing Interests: The authors declare no competing financial interests.

The magnetic order in antiferromagnetic materials is hard to control with external magnetic fields. Using x-ray magnetic linear dichroism microscopy, we show that staggered effective fields generated by electrical current can induce modification of the antiferromagnetic domain structure in microdevices fabricated from a tetragonal CuMnAs thin film. A clear correlation between the average domain orientation and the anisotropy of the electrical resistance is demonstrated, with both showing reproducible switching in response to orthogonally applied current pulses. However, the behavior is inhomogeneous at the submicron level, highlighting the complex nature of the switching process in multidomain antiferromagnetic films.

Antiferromagnets are hard to control by external magnetic fields because of the alternating directions of magnetic moments on individual atoms and the resulting zero net magnetization. However, relativistic quantum mechanics allows for generating current-induced internal fields whose sign alternates with the periodicity of the antiferromagnetic lattice. Using these fields, which couple strongly to the antiferromagnetic order, we demonstrate room-temperature electrical switching between stable configurations in antiferromagnetic CuMnAs thin-film devices by applied current with magnitudes of order 10(6) ampere per square centimeter. Electrical writing is combined in our solid-state memory with electrical readout and the stored magnetic state is insensitive to and produces no external magnetic field perturbations, which illustrates the unique merits of antiferromagnets for spintronics., (Copyright © 2016, American Association for the Advancement of Science.)

Tetragonal CuMnAs is an antiferromagnetic material with favourable properties for applications in spintronics. Using a combination of neutron diffraction and x-ray magnetic linear dichroism, we determine the spin axis and magnetic structure in tetragonal CuMnAs, and reveal the presence of an interfacial uniaxial magnetic anisotropy. From the temperature-dependence of the neutron diffraction intensities, the Néel temperature is shown to be (480 ± 5) K. Ab initio calculations indicate a weak anisotropy in the (ab) plane for bulk crystals, with a large anisotropy energy barrier between in-plane and perpendicular-to-plane directions.

We propose a novel hybrid single-electron device for reprogrammable low-power logic operations, the magnetic single-electron transistor (MSET). The device consists of an aluminium single-electron transistor with a GaMnAs magnetic back-gate. Changing between different logic gate functions is realized by reorienting the magnetic moments of the magnetic layer, which induces a voltage shift on the Coulomb blockade oscillations of the MSET. We show that we can arbitrarily reprogram the function of the device from an n-type SET for in-plane magnetization of the GaMnAs layer to p-type SET for out-of-plane magnetization orientation. Moreover, we demonstrate a set of reprogrammable Boolean gates and its logical complement at the single device level. Finally, we propose two sets of reconfigurable binary gates using combinations of two MSETs in a pull-down network.

Recently discovered relativistic spin torques induced by a lateral current at a ferromagnet/paramagnet interface are a candidate spintronic technology for a new generation of electrically controlled magnetic memory devices. The focus of our work is to experimentally disentangle the perceived two model physical mechanisms of the relativistic spin torques, one driven by the spin-Hall effect and the other one by the inverse spin-galvanic effect. Here, we show a vector analysis of the torques in a prepared epitaxial transition-metal ferromagnet/semiconductor-paramagnet single-crystal structure by means of the all-electrical ferromagnetic resonance technique. By choice of our structure in which the semiconductor paramagnet has a Dresselhaus crystal inversion asymmetry, the system is favourable for separating the torques due to the inverse spin-galvanic effect and spin-Hall effect mechanisms into the field-like and antidamping-like components, respectively. Since they contribute to distinct symmetry torque components, the two microscopic mechanisms do not compete but complement each other in our system.

We demonstrate optical manipulation of the position of a domain wall in a dilute magnetic semiconductor, GaMnAsP. Two main contributions are identified. First, photocarrier spin exerts a spin-transfer torque on the magnetization via the exchange interaction. The direction of the domain-wall motion can be controlled using the helicity of the laser. Second, the domain wall is attracted to the hot spot generated by the focused laser. Unlike magnetic-field-driven domain-wall depinning, these mechanisms directly drive domain-wall motion, providing an optical tweezerlike ability to position and locally probe domain walls.

Magnetization switching at the interface between ferromagnetic and paramagnetic metals, controlled by current-induced torques, could be exploited in magnetic memory technologies. Compelling questions arise regarding the role played in the switching by the spin Hall effect in the paramagnet and by the spin-orbit torque originating from the broken inversion symmetry at the interface. Of particular importance are the antidamping components of these current-induced torques acting against the equilibrium-restoring Gilbert damping of the magnetization dynamics. Here, we report the observation of an antidamping spin-orbit torque that stems from the Berry curvature, in analogy to the origin of the intrinsic spin Hall effect. We chose the ferromagnetic semiconductor (Ga,Mn)As as a material system because its crystal inversion asymmetry allows us to measure bare ferromagnetic films, rather than ferromagnetic-paramagnetic heterostructures, eliminating by design any spin Hall effect contribution. We provide an intuitive picture of the Berry curvature origin of this antidamping spin-orbit torque as well as its microscopic modelling. We expect the Berry curvature spin-orbit torque to be of comparable strength to the spin-Hall-effect-driven antidamping torque in ferromagnets interfaced with paramagnets with strong intrinsic spin Hall effect.

The rich internal degrees of freedom of magnetic domain walls make them an attractive complement to electron charge for exploring new concepts of storage, transport and processing of information. Here we use the tunable internal structure of a domain wall in a perpendicularly magnetized GaMnAsP/GaAs ferromagnetic semiconductor and demonstrate devices in which piezoelectrically controlled magnetic anisotropy yields up to 500% mobility variations for an electrical-current-driven domain wall. We observe current-induced domain wall motion over a wide range of current-pulse amplitudes and report a direct observation and the piezoelectric control of the Walker breakdown separating two regimes with different mobilities. Our work demonstrates that in spin-orbit-coupled ferromagnets with weak extrinsic domain wall pinning, the piezoelectric control allows one to experimentally assess the upper and lower boundaries of the characteristic ratio of adiabatic and non-adiabatic spin-transfer torques in the current-driven domain wall motion.

Recent studies have demonstrated the potential of antiferromagnets as the active component in spintronic devices. This is in contrast to their current passive role as pinning layers in hard disk read heads and magnetic memories. Here we report the epitaxial growth of a new high-temperature antiferromagnetic material, tetragonal CuMnAs, which exhibits excellent crystal quality, chemical order and compatibility with existing semiconductor technologies. We demonstrate its growth on the III-V semiconductors GaAs and GaP, and show that the structure is also lattice matched to Si. Neutron diffraction shows collinear antiferromagnetic order with a high Néel temperature. Combined with our demonstration of room-temperature-exchange coupling in a CuMnAs/Fe bilayer, we conclude that tetragonal CuMnAs films are suitable candidate materials for antiferromagnetic spintronics.

(Ga,Mn)As is at the forefront of spintronics research exploring the synergy of ferromagnetism with the physics and the technology of semiconductors. However, the electronic structure of this model spintronics material has been debated and the systematic and reproducible control of the basic micromagnetic parameters and semiconducting doping trends has not been established. Here we show that seemingly small departures from the individually optimized synthesis protocols yield non-systematic doping trends, extrinsic charge and moment compensation, and inhomogeneities that conceal intrinsic properties of (Ga,Mn)As. On the other hand, we demonstrate reproducible, well controlled and microscopically understood semiconducting doping trends and micromagnetic parameters in our series of carefully optimized epilayers. Hand-in-hand with the optimization of the material synthesis, we have developed experimental capabilities based on the magneto-optical pump-and-probe method that allowed us to simultaneously determine the magnetic anisotropy, Gilbert damping and spin stiffness constants from one consistent set of measured data.

Using atomic force microscopy, we have studied the surface structures of high quality molecular beam epitaxy grown (Ga, Mn)As compound. Several samples with different thickness and Mn concentration, as well as a few (Ga, Mn)(As, P) samples have been investigated. All these samples have shown the presence of periodic ripples aligned along the [110] direction. From a detailed Fourier analysis we have estimated the period (-50 nm) and the amplitude of these structures.

We report a study of the electronic properties of the ferromagnetic semiconductor (Ga,Mn)As using magnetic linear dichroism in the angular dependence of Mn 2p photoemission under hard x-ray excitation. Bulk plasmon loss satellites demonstrate that the probed Mn ions are incorporated deep within the GaAs lattice, while the observed large dichroism indicates that the spectra originate from ferromagnetic substitutional Mn. Simulations of the spectra using an Anderson impurity model show that the ferromagnetic Mn 3d electrons of substitutional Mn in (Ga,Mn)As are intermediate between localized and delocalized.

(Ga, Mn)As and other diluted magnetic semiconductors (DMS) attract a great deal of attention for potential spintronic applications because of the possibility of controlling the magnetic properties via electrical gating. Integration of a ferroelectric gate on the DMS channel adds to the system a non-volatile memory functionality and permits nanopatterning via the polarization domain engineering. This topical review is focused on the multiferroic system, where the ferromagnetism in the (Ga, Mn)As DMS channel is controlled by the non-volatile field effect of the spontaneous polarization. Use of ferroelectric polymer gates in such heterostructures offers a viable alternative to the traditional oxide ferroelectrics generally incompatible with DMS. Here we review the proof-of-concept experiments demonstrating the ferroelectric control of ferromagnetism, analyze the performance issues of the ferroelectric gates and discuss prospects for further development of the ferroelectric/DMS heterostructures toward the multiferroic field effect transistor.

Ferromagnetic resonance is the most widely used technique for characterizing ferromagnetic materials. However, its use is generally restricted to wafer-scale samples or specific micro-magnetic devices, such as spin valves, which have a spatially varying magnetization profile and where ferromagnetic resonance can be induced by an alternating current owing to angular momentum transfer. Here we introduce a form of ferromagnetic resonance in which an electric current oscillating at microwave frequencies is used to create an effective magnetic field in the magnetic material being probed, which makes it possible to characterize individual nanoscale samples with uniform magnetization profiles. The technique takes advantage of the microscopic non-collinearity of individual electron spins arising from spin-orbit coupling and bulk or structural inversion asymmetry in the band structure of the sample. We characterize lithographically patterned (Ga,Mn)As and (Ga,Mn)(As,P) nanoscale bars, including broadband measurements of resonant damping as a function of frequency, and measurements of anisotropy as a function of bar width and strain. In addition, vector magnetometry on the driving fields reveals contributions with the symmetry of both the Dresselhaus and Rashba spin-orbit interactions.

During growth of the dilute p-type ferromagnetic semiconductor Ga1-xMnxAs, interstitial manganese, Mni(2+), is formed when x exceeds 2%. The double donor Mni(2+) compensates the free holes that mediate ferromagnetism. Annealing causes out-diffusion of these interstitials, thereby increasing the Curie temperature. Here, we use cross sectional scanning tunneling microscopy and spectroscopy to visualize the potential landscape which arises due to the clustering of Mni(2+) in annealed p-i-n (GaMn)As-GaAs double barrier heterostructures. We map the local minima in the potential landscape, link them to clusters of individual Mni(2+) ions, and show that the ions are doubly charged.

We analyze microscopically the valence and impurity band models of ferromagnetic (Ga,Mn)As. We find that the tight-binding Anderson approach with conventional parametrization and the full potential local-density approximation+U calculations give a very similar band structure whose microscopic spectral character is consistent with the physical premise of the k·p kinetic-exchange model. On the other hand, the various models with a band structure comprising an impurity band detached from the valence band assume mutually incompatible microscopic spectral character. By adapting the tight-binding Anderson calculations individually to each of the impurity band pictures in the single Mn impurity limit and then by exploring the entire doping range, we find that a detached impurity band does not persist in any of these models in ferromagnetic (Ga,Mn)As.

Background and Purpose: Healthy older living donors (> 50 years) are helping meet increasing demands for kidney transplantation. Live donor grafts perform better than cadaveric donor grafts; however, concern surrounds the expected nephron loss of the donors as well as the relative safety to the donor. We examined the effect age had on living laparoscopic donor and recipient outcomes at a single institution., Patients and Methods: We retrospectively reviewed records of 101 patients who underwent laparoscopic donor nephrectomy (LDN) from October 2001 to December 2005. Twenty-nine (29%) who were aged 50 years or older, denoted as the "older" group, were compared with the remaining 72 (71%) donors who were younger than 50 years and served as controls. Perioperative and follow-up data were analyzed for both groups., Results: The mean age at the time of donation was 36.1 and 54.3 years for control and older donors, respectively (P < 0.001). Baseline mean creatinine level was 0.82 mg/dL for controls and 0.84 mg/dL for older donors (P = 0.78). Complications in controls and the older group were 18% and 17%, respectively. One-year transplant survival was 100% for the controls and 96% for the older group. Average creatinine level at longer follow-up of 19 months for controls and 23 months for the older group (P = 0.34) was 1.22 mg/dL and 1.16 mg/dL, respectively (P = 0.535)., Conclusion: LDN in donors older than 50 years of age appears safe and demonstrates similar outcomes compared with the control cohort of patients younger than 50 years. Age between 50 and 65 years should not exclude a potential donor who otherwise satisfies donor nephrectomy criteria.

Xanthogranulomatous pyelonephritis (XGP) is a chronic inflammatory process that results in replacement of renal and/or perirenal tissue with a diffuse infiltrate of inflammatory cells referred to as xanthoma cells. We present a case of a 49-year-old man with an incidentally discovered renal mass with inferior vena cava (IVC) thrombus, who was found intraoperatively to have a significant inflammatory process involving the posterior wall of his IVC and right renal vein consistent with XGP surrounding a focus of clear cell renal cell carcinoma in the midportion of his right kidney.

Background and Purpose: Although multiple series of helium insufflation-assisted laparoscopic surgery are reported, we encountered difficulty at many levels when arranging a laparoscopic nephrectomy with helium insufflation. We present our experience with attempting to use helium gas as an insufflant and our successful use of argon gas as an adjunct to CO(2) insufflation with a case report as illustration., Materials and Methods: The patient is a 66-year-old man with a progressively enlarging 3.1-cm right renal mass. His history is significant for severe chronic obstructive pulmonary disease, necessitating home oxygen and frequent cycles of steroids. In line with the patient's desire for a minimally invasive procedure, we scheduled a laparoscopic nephrectomy with helium gas. Helium tanks need specialized adapters (yoke) to connect to laparoscopic insufflators; once the yoke was located, we were informed that helium is not approved by the Food and Drug Administration for use as an insufflant and we could not proceed with its use without a full hospital institutional review board review. We elected to use low-pressure CO(2) insufflation augmented by argon gas insufflation via the argon beam coagulator., Results: The patient tolerated the low-pressure CO(2) /argon gas pneumoperitoneum without difficulty. There were no significant changes in the hemodynamic variables throughout the procedure. This patient was extubated at the completion of the procedure, and there were no intraoperative or postoperative complications., Conclusions: Although numerous reports and case series exist regarding the use of helium as an alternate insufflation agent to CO(2), the logistics of obtaining the correct helium yoke and hospital approval are cumbersome for this rarely indicated agent. A far simpler alternative, with similar physiologic effects, is the use of argon gas as an adjunct to CO(2) insufflation, or in lieu of CO(2) insufflation.

We observe a singularity in the temperature derivative drho/dT of resistivity at the Curie point of high-quality (Ga,Mn)As ferromagnetic semiconductors with Tc's ranging from approximately 80 to 185 K. The character of the anomaly is sharply distinct from the critical contribution to transport in conventional dense-moment magnetic semiconductors and is reminiscent of the drho/dT singularity in transition metal ferromagnets. Within the critical region accessible in our experiments, the temperature dependence on the ferromagnetic side can be explained by dominant scattering from uncorrelated spin fluctuations. The singular behavior of drho/dT on the paramagnetic side points to the important role of short-range correlated spin fluctuations.

Multiferroic structures that provide coupled ferroelectric and ferromagnetic responses are of significant interest as they may be used in novel memory devices and spintronic logic elements. One approach towards this goal is the use of composites that couple ferromagnetic and ferroelectric layers through magnetostrictive and piezoelectric strain transmitted across the interfaces. However, mechanical clamping of the films to the substrate limits their response. Structures where the magnetic response is modulated directly by the electric field of the poled ferroelectric would eliminate this constraint and provide a qualitatively higher level of integration, combining the emerging field of multiferroics with conventional semiconductor microelectronics. Here, we report the realization of such a device using (Ga,Mn)As, which is an archetypical diluted magnetic semiconductor with well-understood carrier-mediated ferromagnetism, and a polymer ferroelectric gate. Polarization reversal of the gate by a single voltage pulse results in a persistent modulation of the Curie temperature of the ferromagnetic semiconductor. The non-volatile gating of (Ga,Mn)As has been made possible by applying a low-temperature copolymer deposition technique that is distinct from pre-existing technologies for ferroelectric gates on magnetic oxides. This accomplishment opens a way to nanometre-scale modulation of magnetic semiconductor properties with rewritable ferroelectric domain patterns, operating at modest voltages and subnanosecond times.

We report experimental and theoretical studies of magnetic domain walls in an in-plane magnetized (Ga,Mn)As dilute moment ferromagnetic semiconductor. Our high-resolution electron holography technique provides direct images of domain wall magnetization profiles. The experiments are interpreted based on microscopic calculations of the micromagnetic parameters and Landau-Lifshitz-Gilbert simulations. We find that the competition of uniaxial and biaxial magnetocrystalline anisotropies in the film is directly reflected in orientation dependent wall widths, ranging from approximately 40 to 120 nm. The domain walls are of the Néel type and evolve from near-90 degrees walls at low temperatures to large angle [11[over ]0]-oriented walls and small angle [110]-oriented walls at higher temperatures.

Purpose: To determine differences in the systemic and cell-specific immune response to open and laparoscopic nephrectomy in the porcine model., Materials and Methods: Twenty male pigs (25-40 kg) were vaccinated with human adenovirus containing ovalbumin (Ova) and 3 weeks later underwent a sham procedure (N = 4), laparoscopic nephrectomy (LN)(N = 8), or open nephrectomy (ON) (N = 8). Blood was collected after anesthesia induction and immediately and 24 and 48 hours postoperatively and assayed for complete blood count (CBC), cortisol, and C-reactive protein (CRP). Natural killer (NK) cells were isolated and stimulated in vitro for 48 hours with polyinosinic:polycytidylic acid (Poly I:C) and interleukin (IL)-2 to determine cytotoxic activity. Peripheral blood mononuclear cells (PBMC) were isolated for flow cytometry staining with CD8, CD4, and CD25 markers. Additional PBMCs were stimulated in vitro with Ova and ConA for 48 hours to measure the production of IL-10 and interferon (IFN)-gamma and a thymidine-incorporation assay to determine T-cell proliferation., Results: One animal in the ON group had signs of infection preoperatively and was removed from analysis. The LN took significantly longer than ON or sham nephrectomy (P = 0.002). Blood loss and animal weight were similar in the three groups. The CRP concentration increased more in the ON than the LN and sham-treatment groups in the first 48 hours (P = 0.01). No statistical differences were seen in the elevation of white blood cells or cortisol concentration. All groups demonstrated a decrease in the cytotoxic activity of NK cells postoperatively, with a significantly greater decrease in the sham-treated animals (P = 0.004). The LN group demonstrated greater T-cell activation than the ON and sham-treatment groups with both CD4(+) (P = 0.002) and CD8(+) (P = 0.028) cells increasing their expression of the activation marker CD25. The thymidine-incorporation assay demonstrated decreased T-cell proliferation in the ON group when stimulated with ConA (P = 0.014). Production of IL-10 decreased in the sham-treated and LN animals while increasing after ON. There was no difference in IFN-gamma among the groups., Conclusions: In a porcine model, ON produces higher CRP concentrations postoperatively, a larger decrease in T-cell proliferation ability, and more IL-10 activity than LN or sham treatment. Animals undergoing LN demonstrated greater T-cell activation postoperatively. White blood cell counts, serum cortisol concentration, and production of IFN-gamma were similar among the groups. These findings suggest ON causes greater immune suppression than LN in the porcine model.

We explore the basic physical origins of the noncrystalline and crystalline components of the anisotropic magnetoresistance (AMR) in (Ga,Mn)As. The sign of the noncrystalline AMR is found to be determined by the form of spin-orbit coupling in the host band and by the relative strengths of the nonmagnetic and magnetic contributions to the Mn impurity potential. We develop experimental methods yielding directly the noncrystalline and crystalline AMR components which are then analyzed independently. We report the observation of an AMR dominated by a large uniaxial crystalline component and show that AMR can be modified by local strain relaxation. Generic implications of our findings for other dilute moment systems are discussed.

Objectives: To investigate the success rates and quality-of-life outcomes with the male bulbourethral sling using the validated Male Urogenital Distress Inventory (MUDI) and Male Urinary Symptom Impact Questionnaire (MUSIQ). These validated incontinence questionnaires for men have not been reported in the sling population., Methods: A total of 31 consecutive patients underwent placement of a male bulbourethral bone-anchoring sling from October 2002 through May 2005. The preoperative information included history and physical examination, pad history, urodynamic findings, and MUDI and MUSIQ results. Postoperatively, the patients were evaluated clinically and completed a MUDI and MUSIQ every 6 months., Results: Of the 31 patients, 24 completed the questionnaires and follow-up protocol. Of the other 7 patients, 4 underwent sling removal and 3 were lost to follow-up. The average follow-up time was 15 months (range 9 to 21). After surgery, the pad use decreased from a median of 3.7 pads/day (range 1 to 12) to 1.3 pads/day (range 0 to 6). Of the 24 analyzed patients, 18 (75%) were dry or using 1 pad or less per day, and 9 (38%) no longer needed pads. Subjectively, 75% of the patients were satisfied. The mean MUDI and MUSIQ scores decreased from 56.8 and 29.9 preoperatively to 44.8 (P <0.0001) and 14.6 (P = 0.002) after sling placement, respectively. When all 31 patients were included, our clinical success rate of 1 pad/day or less decreased to 58%., Conclusions: Of the 24 patients with follow-up data, 75% were satisfied and were clinically cured. A significant improvement was seen after surgery in the MUDI and MUSIQ scores, severity of incontinence, and average pad use. The MUDI and MUSIQ scores paralleled patient satisfaction and clinical success after male bulbourethral sling placement.

We propose to replace Ga in (Ga,Mn)As with Li and Zn as a route to high Curie temperature, carrier mediated ferromagnetism in a dilute moment n-type semiconductor. Superior material characteristics, rendering Li(Zn,Mn)As a realistic candidate for such a system, include high solubility of the isovalent substitutional Mn impurity and carrier concentration controlled independently of Mn doping by adjusting Li-(Zn,Mn) stoichiometry. Our predictions are anchored by ab initio calculations and comparisons with the familiar and directly related (Ga,Mn)As, by the physical picture we provide for the exchange interaction between Mn local moments and electrons in the conduction band, and by analysis of prospects for the controlled growth of Li(Zn,Mn)As materials.

We describe a rare occurrence of an 11-month-old male infant with metastatic bilateral testicular neuroblastoma presenting with bilateral scrotal swelling.

We observe low-field hysteretic magnetoresistance in a (Ga,Mn)As single-electron transistor which can exceed 3 orders of magnitude. The sign and size of the magnetoresistance signal are controlled by the gate voltage. Experimental data are interpreted in terms of electrochemical shifts associated with magnetization rotations. This Coulomb blockade anisotropic magnetoresistance is distinct from previously observed anisotropic magnetoresistance effects as it occurs when the anisotropy in a band structure derived parameter is comparable to an independent scale, the single-electron charging energy. Effective kinetic-exchange model calculations in (Ga,Mn)As show chemical potential anisotropies consistent with experiment and ab initio calculations in transition metal systems suggest that this generic effect persists to high temperatures in metal ferromagnets with strong spin-orbit coupling.

Remarkably anisotropic Mn L2,3 x-ray magnetic circular dichroism spectra from the ferromagnetic semiconductor (Ga,Mn)As are reported. States with cubic and uniaxial symmetry are distinguished by careful analysis of the angle dependence of the spectra. The multiplet structures with cubic symmetry are qualitatively reproduced by calculations for an atomiclike d5 configuration in tetrahedral environment, and show zero anisotropy in the orbital and spin moments within the experimental uncertainty. However, hybridization with the host valence bands is reflected by the presence of a preedge feature with a uniaxial anisotropy and a marked dependence on the hole density.

We demonstrate that the interplay of in-plane biaxial and uniaxial anisotropy fields in results in a spin reorientation transition and an anisotropic ac susceptibility which is fully consistent with a simple single-domain model. The uniaxial and biaxial anisotropy constants vary, respectively, as the square and fourth power of the spontaneous magnetization across the whole temperature range up to . The weakening of the anisotropy at the transition may be of technological importance for applications involving thermally assisted magnetization switching.

We report a large tunneling anisotropic magnetoresistance (TAMR) in (Ga,Mn)As lateral nanoconstrictions. Unlike previously reported tunneling magnetoresistance effects in nanocontacts, the TAMR does not require noncollinear magnetization on either side of the constriction. The nature of the effect is established by a direct comparison of its phenomenology with that of normal anisotropic magnetoresistance (AMR) measured in the same lateral geometry. The direct link we establish between the TAMR and AMR indicates that TAMR may be observable in other materials showing room temperature AMR and demonstrates that the physics of nanoconstriction magnetoresistive devices can be much richer than previously thought.

We present a combined theoretical and experimental study of the ferromagnetic semiconductor (Ga,Mn)As which explains the remarkably large changes observed on low-temperature annealing. Careful control of the annealing conditions allows us to obtain samples with ferromagnetic transition temperatures up to 159 K. Ab initio calculations, in situ Auger spectroscopy, and resistivity measurements during annealing show that the observed changes are due to out diffusion of Mn interstitials towards the surface, governed by an energy barrier of 0.7-0.8 eV. Electric fields induced by Mn acceptors have a significant effect on the diffusion.