X-Ray Magnetic Circular Dichroism in Altermagnetic α-MnTe.

Altermagnetism is a recently identified magnetic symmetry class combining characteristics of conventional collinear ferromagnets and antiferromagnets, that were regarded as mutually exclusive, and enabling phenomena and functionalities unparalleled in either of the two traditional elementary magnetic classes. In this work we use symmetry, ab initio theory, and experiments to explore x-ray magnetic circular dichroism (XMCD) in the altermagnetic class. As a representative material for our XMCD study we choose α-MnTe with compensated antiparallel magnetic order in which an anomalous Hall effect has been already demonstrated. We predict and experimentally confirm a characteristic XMCD line shape for compensated moments lying in a plane perpendicular to the light propagation vector. Our results highlight the distinct phenomenology in altermagnets of this time-reversal symmetry breaking response, and its potential utility for element-specific spectroscopy and microscopy.

Influence of an Anomalous Temperature Dependence of the Phase Coherence Length on the Conductivity of Magnetic Topological Insulators.

Magnetotransport constitutes a useful probe to understand the interplay between electronic band topology and magnetism in spintronic devices. A recent theory of Lu and Shen [Phys. Rev. Lett. 112, 146601 (2014)PRLTAO0031-900710.1103/PhysRevLett.112.146601] on magnetically doped topological insulators predicts that quantum corrections Δκ to the temperature dependence of conductivity can change sign across the Curie transition. This phenomenon has been attributed to a suppression of the Berry phase of the topological surface states at the Fermi level, caused by a magnetic energy gap. Here, we demonstrate experimentally that Δκ can reverse its sign even when the Berry phase at the Fermi level remains unchanged. The contradictory behavior to theory predictions is resolved by extending the model by Lu and Shen to a nonmonotonic temperature scaling of the inelastic scattering length showing a turning point at the Curie transition.

High magnetic field test of the ITER outer vessel steady-state magnetic field Hall sensors at ITER relevant temperature.

The ITER outer vessel steady-state magnetic field sensor diagnostics consist of sixty sensor units. Each sensor unit features a pair of ceramic-metal Hall sensors with a sensing layer made of bismuth. The sensors were tested simultaneously in the magnetic field ranging from -12 T to +12 T at the temperature range from 27 to 127 °C. The Hall coefficient and magnetoresistance of the bismuth layer related to the sensors were identified. In the sensor operating conditions, the Hall coefficient dependence on temperature was fitted with an exponential function with a relative error of less than 0.08%, and the dependence on the magnetic field was fitted with a Gaussian-like function with a relative error of less than 0.11%. An alternative expression based on the physical understanding of the free charge carrier transport in semimetals was derived to describe the dependence of the Hall coefficient on the magnetic field, and its fitting error of 1.2 mT in terms of the magnetic field measurement has met the ITER measurement accuracy requirements.

Multiple-stable anisotropic magnetoresistance memory in antiferromagnetic MnTe.

Commercial magnetic memories rely on the bistability of ordered spins in ferromagnetic materials. Recently, experimental bistable memories have been realized using fully compensated antiferromagnetic metals. Here we demonstrate a multiple-stable memory device in epitaxial MnTe, an antiferromagnetic counterpart of common II-VI semiconductors. Favourable micromagnetic characteristics of MnTe allow us to demonstrate a smoothly varying zero-field antiferromagnetic anisotropic magnetoresistance (AMR) with a harmonic angular dependence on the writing magnetic field angle, analogous to ferromagnets. The continuously varying AMR provides means for the electrical read-out of multiple-stable antiferromagnetic memory states, which we set by heat-assisted magneto-recording and by changing the writing field direction. The multiple stability in our memory is ascribed to different distributions of domains with the Néel vector aligned along one of the three magnetic easy axes. The robustness against strong magnetic field perturbations combined with the multiple stability of the magnetic memory states are unique properties of antiferromagnets.

Relativistic Néel-order fields induced by electrical current in antiferromagnets.

We predict that a lateral electrical current in antiferromagnets can induce nonequilibrium Néel-order fields, i.e., fields whose sign alternates between the spin sublattices, which can trigger ultrafast spin-axis reorientation. Based on microscopic transport theory calculations we identify staggered current-induced fields analogous to the intraband and to the intrinsic interband spin-orbit fields previously reported in ferromagnets with a broken inversion-symmetry crystal. To illustrate their rich physics and utility, we consider bulk Mn(2)Au with the two spin sublattices forming inversion partners, and a 2D square-lattice antiferromagnet with broken structural inversion symmetry modeled by a Rashba spin-orbit coupling. We propose an antiferromagnetic memory device with electrical writing and reading.

An antidamping spin-orbit torque originating from the Berry curvature.

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.

Spin-orbit-driven ferromagnetic resonance.

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.

Curie point singularity in the temperature derivative of resistivity in (Ga,Mn)As.

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.

Anisotropic magnetoresistance components in (Ga,Mn)As.

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.

[Personal experience in treatment of urolithiasis using the MEDILIT M6 extracorporeal lithotriptor]. / Nase zkusenosti s lécbou urolitiázy extrakorporálním litotryptorem MEDILIT M6.

The authors report on their experience with the destruction of kidney stones with the lithotriptor MEDELIT M6 of Medipo Co. BRNO on the development of which they participated. They checked 878 patients where the instrument was used and where the condition of a half-year interval after the operation had been met. In these patients 119 operations were made 87% of which were successful. No serious complications occurred; after operation they observed in 17% of the patients complications ensuing from a block of the ureter by the passing stones. The extracorporeal lithotriptor MEDELIT M6 is a reliable instrument with a low rate of defects and cheap operation which makes accurate X-ray and sonographic focusing on the stone possible as well as adequate disintegration of the concrement without damaging surrounding tissues. It is comparable with instruments of the same generation manufactured abroad.

A comparison of various methods for cooling the kidney.

Various methods for achieving preoperative renal hypothermia were tested and evaluated. A kidney immersed in an oil bath solution at 4 degrees C resulted in the highest rate of contact hyperthermia at a determined safe temperature of cooling medium. The acquired basic temperature curve served as a model for the comparison of other methods tested. The results showed that perfusion hypothermia is most rapid but this method is limited by the number and state of the renal arteries and displays all the risks associated with cannulation of arteries. Covering the kidney with crushed ice led to a sufficiently rapid decrease in temperature but lack of regulation carries the danger of renal damage caused by excessive temperature reduction. The disadvantages of these methods were eliminated using a device developed and tested by the authors.

Kidney temperature measurement. Thermistors for temperature measurement.

During a study of the protective effects of cold on kidney cells under conditions of interrupted blood circulation, it was found that attention must be paid to the temperature of kidney tissue in order to prevent cell damage caused by an excessively reduced temperature. The authors correspondingly developed an instrument for the measurement of kidney tissue temperature where thermal sensors located in a needle are able to measure deep temperature in live tissue under conditions of external hypothermia. Thermal sensors were also placed in a hypothermal coil for contact measurement of surface temperature of a cooled kidney and in a duct for supply of cooling medium into a coil. Construction of these devices is described and basic the characteristics of the thermistor and thermocouple sensors for temperature measurement are presented. After evaluation of advantages of the tested sensors, indications regarding their application are given.

A revised instrument for the regulated external cooling of the kidney.

The authors describe the instrument they have developed for the regulated external cooling of the kidney. This consists of a cooling thermostat fitted with a circulating pump, coils of their own construction for the surface cooling of the kidney and equipped with sensors for the measurement of kidney surface temperature, tube connectors, and a sensor for the measurement of the cooling medium temperature. A cooling liquid is supplied by means of a circulating pump from a thermostat through elastic tubes into the flow channels of the cooling coils. The temperature of the coolant is recorded by means of a thermistor sensor built into the system of tubes while the temperature of the kidney surface itself is monitored by a sensor installed in a coil. This permits the regulation of both the rate and depth of temperature reduction in order to prevent possible damage to the kidney caused by excessive temperature reduction. The efficiency and safety of this instrument were verified both experimentally and clinically.

A revised coil for the external cooling of the kidney.

The authors describe a coil they have developed for contact peroperative hypothermia of the kidney. This new type of coil eliminates the disadvantages of existing cooling coils, namely slow thermal transfer from kidney to cooling agent due to imperfect contact between the coil and the concave surface of the kidney, use of an inadequately conductive material and thermal losses from the outer surface of the coil. Special features of the coil described here include its construction to match the contours of the kidney, isolation of external shell to reduce thermal losses and continuous monitoring of renal tissue to reduce the danger of overcooling.

Protection of kidney cell against ischaemic damage by decreased kidney temperature.

At normal body temperature, kidney cells are highly sensitive to hypoxia. However, a bloodless operative field is advantageous in some interventions on the kidney. Kidney cells can be protected against the damage that might occur once blood flow has been interrupted pharmacologically or physically by reducing their temperature. The authors compare several methods for achieving renal hypothermia, including a method based on a device they developed themselves to eliminate defects found in existing equipment. The thermal curve obtained when the kidney is immersed in an oil bath cooled to 5 degrees C served as a model for other methods. Using the revised coil developed by the authors, renal hypothermia was achieved safely and efficiently. A combination of pharmacological and physiological methods is preferrable however in order to potentiate the effect of decreased temperature. This method was tested experimentally and then successfully applied in clinical practice.

Priapism: a urological emergency.

The authors describe their experience obtained in the treatment of 25 patients with priapism. The results are analysed on the basis of recent physiological concepts and immediate surgery is recommended. Priapism is a urological emergency and requires urgent treatment. The method commonly used at their clinic is described.

[An uncommon cause of testalgia]. / Méne castá prícina testalgií.

Ten men aged 30-55 years suffered for many years from unilateral testalgia without subjective vertebrogenic complaints, and comprehensive urological examination did not reveal the cause of pain. Detailed functional examination of the spine revealed in all patients homolateral blocks of the Th-L transition, in nine men spasms of the musculus psoas, in five moreover a block of the SI synchondrosis on the same side. After a single or repeated release of the block the testalgias receded.

[Fibroepithelial ureteral polyps]. / Fibroepiteliální polypy mocovodu.

Fibroepithelial polyps of the ureter are rare. They have as a rule a benign character and threaten the patient by obstruction of the efferent urinary pathways. The author presents an account in Olomouc. In the discussion he deals with the problem of diagnosis and treatment of this disease.