Effect Of Spin Orientation Research Articles

Bulk photospin effect: Calculation of electric spin susceptibility to second order in an electric field

We compute the electric spin susceptibility of Bloch electrons with spin-orbit coupling to second order. We find that it is possible to generate a nonequilibrium spin polarization in the bulk of non-magnetic inversion-symmetric materials using linearly polarized electric fields, but the process depends on interband coherence and produces heating. It may be possible to avoid heating with circular polarization in certain scenarios. The standard Edelstein effect and spin orientation effects are recovered in appropriate limits within the formalism. Finally, the electric spin susceptibility of metals has contributions proportional to spin multipole moments of the Fermi sea that dominate the low frequency spin response.

Artificial magnetism in a carbon diamond nanolattice with the spin orientation effect

In this paper, we investigate the spin orientation effects on the magnetic properties of the Carbon diamond nanolattice (CDNL) by using Kaneyoshi approach (KA) within the effective field theory. In our calculations, we use the normalized lattice constant (na=3.566=a/1A0) which is obtained from the real lattice constant (a=3.566A0) of the CDNL. The CDNL has three different magnetic atoms according to nearest-neighbor, and they are defined as corner atoms (mc), face atoms (mf) and inner atoms (mi). For mc, mf and mi, the CDNL has eight spin orientations as +++ (↑↑↑), −++ (↓↑↑), ++− (↑↑↓), −+− (↓↑↓), −−+ (↓↓↑), −−− (↓↓↓), +−− (↑↓↓) and +−+ (↑↓↑), respectively. We find that the CDNL has two kinds of critical temperature behaviors, we call them as high critical temperature behavior (HCTB) for the first four spin orientations and low critical temperature behavior (LCTB) for the second four spin orientations. However, the CDNL exhibits ferromagnetic (FM), antiferromagnetic (AFM), superconductivity (SC), discontinuous diamagnetic (DM) and discontinuous paramagnetic (PM) hysteresis behaviors according to the spin orientation of its atoms. Therefore, we suggest that it is possible to obtain different magnetic behaviors and artificial magnetism from the Carbon and Carbon-based materials with the spin orientations of their atoms.

The magnetic structure of β-cobalt hydroxide and the effect of spin-orientation.

Synchrotron X-ray and neutron diffraction experiments at various temperatures, down to 3 K, along with ab initio calculations, are carried out to elucidate the magnetic order of layered β-cobalt-hydroxide. This combination of techniques allows for the unambiguous assignment of the magnetic structure of this material. Our results confirm that below the Néel temperature high-spin cobalt centers are ferromagnetically coupled within a layer, and antiferromagnetically coupled across layers (magnetic propagation vector k = (0,0,½)), in agreement with the indirect interpretation based on magnetic susceptibility measurements. A paramagnetic/antiferromagnetic transition is observed at around 15 K. Moreover, the thermal expansion behavior along the c-lattice direction, perpendicular to the layers, shows an inflection slightly above this temperature, at around 30 K. The neutron diffraction patterns and the non-collinear DFT+U calculations indicate that the magnetization forms an angle of about 35° with the cobalt planes. In particular, for an isolated ferromagnetic layer, the electronic structure calculations reveal sharp cusps on the potential energy surface when the spins point parallel or perpendicular to the planes, suggesting that the ferromagnetic superexchange mechanism is strongly sensitive to the orientation of the magnetic moment.

Large-amplitude spin oscillations triggered by nonequilibrium strongly correlatedt2gelectrons

Laser-induced ultrafast (fs) magnetization experiments in antiferromagnets have recently attracted large attention, paving the road for inherently fast spin dynamics in the THz regime without invoking stray fields. The technical importance is emphasized by the rising new research field of antiferromagnetic (AFM) spintronics, where superexchange-dominated strongly correlated compounds provide an interesting materials playground. An intriguing question is whether the Coulomb interaction may be a key to control AFM order on ultrafast time scales. Therefore, we study (de)magnetization processes in a time-dependent multiorbital Hubbard model, focusing on $t_{2g}$ electrons in a wider doping range. Depending on filling, we reveal large-amplitude spin oscillations via interaction quenches from the antiferromagnetic or paramagnetic state. Nonequilibrium ultrafast spin-orientation effects in prominent correlated transition-metal oxides are therefrom predicted.

Black-hole–neutron-star mergers at realistic mass ratios: Equation of state and spin orientation effects

Black-hole--neutron-star mergers resulting in the disruption of the neutron star and the formation of an accretion disk and/or the ejection of unbound material are prime candidates for the joint detection of gravitational-wave and electromagnetic signals when the next generation of gravitational-wave detectors comes online. However, the disruption of the neutron star and the properties of the postmerger remnant are very sensitive to the parameters of the binary (mass ratio, black-hole spin, neutron star radius). In this paper, we study the impact of the radius of the neutron star and the alignment of the black-hole spin on black-hole--neutron-star mergers within the range of mass ratio currently deemed most likely for field binaries (${M}_{\mathrm{BH}}\ensuremath{\sim}7{M}_{\mathrm{NS}}$) and for black-hole spins large enough for the neutron star to disrupt (${J}_{\mathrm{BH}}/{M}_{\mathrm{BH}}^{2}=0.9$). We find that (i) In this regime, the merger is particularly sensitive to the radius of the neutron star, with remnant masses varying from $0.3{M}_{\mathrm{NS}}$ to $0.1{M}_{\mathrm{NS}}$ for changes of only 2 km in the NS radius; (ii) $0.01{M}_{\ensuremath{\bigodot}}--0.05{M}_{\ensuremath{\bigodot}}$ of unbound material can be ejected with kinetic energy $\ensuremath{\gtrsim}{10}^{51}\text{ }\text{ }\mathrm{ergs}$, a significant increase compared to low mass ratio, low spin binaries. This ejecta could power detectable postmerger optical and radio afterglows. (iii) Only a small fraction of the Advanced LIGO events in this parameter range have gravitational-wave signals which could offer constraints on the equation of state of the neutron star (at best $\ensuremath{\sim}3%$ of the events for a single detector at design sensitivity). (iv) A misaligned black-hole spin works against disk formation, with less neutron-star material remaining outside of the black hole after merger, and a larger fraction of that material remaining in the tidal tail instead of the forming accretion disk. (v) Large kicks ${v}_{\mathrm{kick}}\ensuremath{\gtrsim}300\text{ }\text{ }\mathrm{km}/\mathrm{s}$ can be given to the final black hole as a result of a precessing black-hole--neutron-star merger, when the disruption of the neutron star occurs just outside or within the innermost stable spherical orbit.

Spin orientation by electric current in (110) quantum wells

We develop a theory of spin orientation by electric current in (110)-grown semiconductor quantum wells. The controversy in the factor of 2 from two existing approaches is resolved by pointing out the importance of energy relaxation in this problem. The limiting cases of fast and slow energy relaxation relative to spin relaxation are considered for asymmetric (110) quantum wells. For symmetrically doped structures the effect of spin orientation is shown to exist due to random spatial variation of the Rashba spin-orbit splitting. We demonstrate that the spin orientation depends strongly on the correlation length of this random spin-orbit field as well as on the ratio of the energy and spin relaxation rates. The time-resolved kinetics of spin polarization by electric current is also governed by the correlation length being not purely exponential at slow energy relaxation. Electrical spin orientation in two-dimensional topological insulators is calculated and compared with the spin polarization induced by the magnetic field.

Superconducting alloys with paramagnetic impurities (part II) magnetization and upper critical fields of LaAl 2 with dilute Gd impurities

Magnetization and AC susceptibility were made on single- and polycrystalline samples of LaAl 2 doped with Gd in the concentration range 0⩽ n I⩽0.7 at%. The depression of T c with Gd content is found to be in excellent agreement with previous experimental work. Concerning the temperature dependence of H c2, peaks at low temperatures (⋍400mK) and downward curvatures towards T=0 have been observed. The upper critical field of the clean material can be explained quantitatively in terms of anisotropic Eliashberg theory using 〈 a 2 〉 =0.01 for the electron-phonon coupling anisotropy parameter and 〈 b 2 〉 =0.16 for the anisotropy of the Fermi velocity. With these values and the generalized phonon density of states reported by Yeh et al. excellent agreement between theory and experiment was achieved. Furthermore, results on the Gd doped materials can be explained quantitatively on the basis of strong coupling theory, if spin orientation effects of the Gd atoms are included in the theoretical treatment.

Magnetization and upper critical fields of LaAl 2 with dilute Gd impurities

Abstract Single- and polycrystalline samples of LaAl2 doped with Gd in the concentration range 0 ⩽ c ⩽ 0.7 at% have been investigated by magnetization and ac susceptibility measurements. The depression of Tc with Gd concentration is in agreement with previous experimental work. Concerning the temperature dependence of Hc2, peaks at intermediate temperatures (∼400 mK) and downward curvatures towards T=0 are observed. The clean limit results can be explained quantitatively in terms of anisotropic Eliashberg theory for the upper critical field, with anisotropy parameters 〈a2〉 = 0.01 for the electron-phonon-coupling and 〈b2〉 = 0.16 for the Fermi velocity. Excellent agreement between theory and experiment can also be achieved for the Gd-doped materials, if spin orientation effects of the Gd atoms are included in the theoretical treatment.

Spin orientation effects of shallow electrons induced by magnetization in transition metal surfaces

From infrared reflection measurements of transition metal surfaces it has been found that the profile is sensitively changed by both magnetization and demagnetization. In particular, the longer wavelength side of the reflection edge induced at the 7 – 15 μm region by magnetization with about 300 G is attributed to shallow electrons which are strongly spin oriented. The shorter wavelength side of the edge is due to mixed electrons which are rather weakly spin oriented. The effect of the three types of edge distribution indicates that the interface between the continuum and the mixed level is sensitive to the degree of magnetization; the degree of variation of the magnetic oscillator is estimated from the Nf-R curve to be within the range 10 21 cm -3 - 10 24cm -3.

Effect of spin orientation on drawing of wet-spun fibers

A previous study has shown that the draw stress of wet-spun acrylic fibers is affected by the orientation acquired in the spin bath, and a tentative mathematical treatment was proposed which employs an analogy with two-stage drawing. In this picture, the spin bath orientation is characterized by an effective draw ratio ℛs, the orientation draw is characterized by ℛ, and the total draw ratio ℛt equals ℛℛs. This concept is developed more extensively in this paper. New data are presented on both acrylic and modacrylic fibers which support the validity of this treatment and also demonstrate how spin orientation is correlated with the take-up speed/free velocity ratio. Absolute values for the effective spin orientation are calculated. Results from round spinneret holes and one-slot hole are discussed with observations on shape retention.