Spin incommensurability and two phase competition in cobaltites

The perovskite LaCoO3 evolves from a nonmagnetic Mott insulator to a spin cluster ferromagnet (FM) with the substitution of Sr2+ for La3+ in La1-xSrxCoO3. The clusters increase in size and number with x and the charge percolation through the clusters leads to a metallic state. Using elastic neutron scattering on La1-xSrxCoO3 single crystals, we show that an incommensurate spin superstructure coexists with the FM spin clusters. The incommensurability increases continuously with x, with the intensity rising in the insulating phase and dropping in the metallic phase as it directly competes with the commensurate FM, itinerant clusters. The spin incommensurability arises from local order of Co3+-Co4+ clusters but no long-range static or dynamic spin stripes develop. The coexistence and competition of the two magnetic phases explain the residual resistivity at low temperatures in samples with metalliclike transport.     

Determination of charge states of cobalt ions in nanostructured GdBaCo2O5.5 cobaltites by means of X-ray absorption spectroscopy

Physics of the Solid State - X-ray absorption spectroscopy has been applied for a characterization of charge states of cobalt ions of nanostructured GdBaCo2O5.5 complex oxides. The analysis of...     

Spin diffusion and relaxation in dilute magnetic alloys: Electron-electron interaction

Diffusion and relaxation of conduction electrons is studied without making the usual approximation that the spin-orbit scattering be smaller than the impurity potential scattering. Renormalization of impurity vertices by the electron-electron interaction reduces the potential, enhances the s-d, but does not affect the spin-orbit scattering cross-section.     

Spin field emission and state switching in a magnetic tunnel junction

The phenomena of spin tunneling and spin torque transfer between magnetic layers of a tunnel spin-valve setup under weak and strong field emissions of spin-polarized electrons are considered. Bifurcational features of changes in the macrospin states under the impact of a tunnel current are discussed for varying directions of the spin-polarization vector.     

Dome-shaped magnetic phase diagram of thermoelectric layered cobaltites

Using muon spin spectroscopy we have found that, for both NaxCoO(2) (0.6相似文献   

Co离子注入TiO2薄膜的显微结构和磁性研究

利用直流磁控溅射技术在玻璃衬底上沉积了TiO₂薄膜,并对其进行了Co离子注入,最后在真空中500 ℃退火50 min,得到系列薄膜样品. 利用剥离-分散方法制备了薄膜的透射电镜样品,并用扫描电镜(SEM)、X射线能量散射谱(EDX)和高分辨透射电镜(HRTEM)对样品做了近似原位观察,研究了薄膜样品中不同Co离子注入深度的成分分布和显微结构. 结果表明,薄膜呈锐钛矿结构,Co元素主要分布在薄膜表层,Co离子的注入使TiO₂薄膜的晶粒被部分破坏,并形成CoO,而5 关键词： 2薄膜')" href="#">Co注入TiO₂薄膜 电镜原位观察 室温铁磁性     

The magnetic state of diamagnetically diluted antiferromagnetic cobalt and nickel monoxide

The nearest neighbour J₁(x) and the next-neighbour super-exchange J₂(x) interactions are evaluated by using the mean field theory for Mg1−xBxO (B=Co and Ni) systems. The magnetic energy E(x) is obtained. A magnetic phase diagram of the Mg1−xBxO (B=Co and Ni) solid solutions with 0?x?1 is drawn by high-temperature series expansions (HTSE) combined with the Padé approximants method (PA). The critical exponents associated with the magnetic susceptibility (γ) and with the correlation length (ν) are deduced in order phase.     

Stopping of slow ions in electron gas with magnetic interaction

The electronic stopping and straggling of low velocity point charge in the electron gas subjected to magnetic ordering is analysed within the linear response theory. The electrons were described by the Lindhard dielectric function ?(k,ω)$\mathrm{?}(\mathbf{k},\omega )$. The magnetic interactions were included in the model along the Stoner treatment of itinerant electrons. The effect caused by phase transition was shown to be negligible comparing to the experimental result.     

Critical currents and the critical state in superconductors with magnetic ions

The critical state model is used to derive equations that relate the additional magnetic moment (ΔM) produced by the flux pinning to the critical current density (J_c) measured in transport measurements. The equations derived for conventional superconductors can be used for superconductors that contain magnetic ions, if ΔM is replaced by ΔM/(1 + χ′(H)) where χ′(H) is the differential susceptibility. In the critical state, the field gradient has contributions from both the macroscopic supercurrents and the Amperian currents from the magnetic ions. Magnetic measurements are sensitive to both contributions. Transport measurements only characterise the macroscopic supercurrents. For superconductors which contain rare-earth elements, the J_c values calculated using hysteretic magnetisation measurements without including the term χ′(H), can be in error by factors of 7.     

Exchange interaction of S state ions with charge carriers in SnTe

ESR investigations of Mn, Eu and Gd in highly degenerate SnTe - a p-type semiconductor with metallic behaviour - prove the existence of an exchange interaction between localized magnetic moments and charge carriers. The ratio of the exchange parameters J_Mn and J_Eu between charge carriers and Mn or Eu ions, respectively, amounts to |J_Mn/J_Eu| = 8 ± 1.5. The consequence this result has on long range spin-spin interaction via charge carriers as well as on hyperfine interaction is discussed.     

Characterization of n-GaN dilute magnetic semiconductors by cobalt ions implantation at high-fluence

In this study, we present the structural and magnetic characteristics of cobalt ions implantation at a high-fluence (5×10¹⁶ cm⁻²) into n-GaN epilayer of thickness about 1.6 μm. The n-GaN was grown on sapphire by metal organic chemical vapor deposition (MOCVD). Rutherford backscattering channeling was used for the structural study. After implantation, samples were annealed at 700, 800 and 900 °C by rapid thermal annealing in ambient N₂. XRD measurements did not show any secondary phase or metal related-peaks. High resolution X-ray diffraction (HRXRD) was performed as well to characterize structures. Well-defined hysteresis loops were observed at 5 K and room temperature using alternating gradient magnetometer AGM and Superconducting Quantum Interference Device (SQUID) magnetometer. Temperature-dependent magnetization indicated magnetic moment at the lowest temperatures and retained magnetization up to 380 K for cobalt-ion-implanted samples.     

Magnetic properties of cobaltites doped with chromium,gallium, and iron ions

The magnetic and magnetotransport properties of cobaltites La_0.5Sr_0.5Co_1–xMe_xO₃ (Me = Cr, Ga, Fe) have been studied. The initial compound (x = 0) is a ferromagnet with T_C = 247 K and a saturation magnetization close to 2μ_B per formula unit. It has ben shown that chromium substitution (x = 0.2) decreases the spontaneous magnetization to 0.3μ_B, while the iron substitution (x = 0.2) does not change the magnetization. The obtained data have been interpreted in a model of positive superexchange interactions between cobalt and iron and negative superexchange interactions between cobalt and chromium.     

A singlet state prepared with resonant interaction via trapped ions

A simple scheme for the generation of the three-qutrit Λ-type singlet state with resonant interaction via trapped ions is proposed. In the present proposal, the required interaction time is very short due to resonant interaction. The present proposal may be realized based on the current technologies. We also note that the three-ion three-level maximally entangled state can be generated via resonant interaction in one step.     

Effect of cobalt impurity ions on the magnetic and electrical properties of iron monosilicide crystals

The results of experimental investigations of Fe_{1 − x} Co _x Si crystals in the impurity limit with x = 0.001, 0.005, and 0.01 are reported. The temperature and field dependences of the magnetic susceptibility have been studied. According to the experimental data, the introduction of cobalt impurity leads to a change in the energy structure, which is most pronounced in a change in the electrical properties. The temperature, field, and concentration dependences of the resistivity have been measured. The results have been interpreted in the framework of the Kondo model.     

Spin and magnetic moment of 33Mg: evidence for a negative-parity intruder ground state

We report on the first determination of the nuclear ground-state spin of 33Mg, I=3/2, and its magnetic moment, mu= -0.7456(5) mu(N), by combining laser spectroscopy with nuclear magnetic resonance techniques. These values are inconsistent with an earlier suggested 1 particle-1 hole configuration and provide evidence for a 2 particle-2 hole intruder ground state with negative parity. The results are in agreement with an odd-neutron occupation of the 3/2 [321] Nilsson orbital at a large prolate deformation. The discussion emphasizes the need of further theoretical and experimental investigation of the island of inversion, a region previously thought to be well understood.     

Spin–lattice relaxation phenomena in the magnetic state of a suggested Weyl semimetal CeAlGe

ABSTRACT

In this work, we report the results of DC susceptibility, AC susceptibility and related technique, resistivity, transverse and longitudinal magnetoresistance and heat capacity on polycrystalline magnetic semimetal CeAlGe. This compound undergoes antiferromagnetic type ordering around 5.2 K (T¹). Under the application of external magnetic fields, parallel alignment of magnetic moments is favoured above 0.5?T. At low field and temperature, frequency and AC field amplitude response of AC susceptibility indicate the presence of spin–lattice relaxation phenomena. The observation of spin–lattice interaction suggests the presence of the Rashba–Dresselhaus spin–orbit interaction which is associated with inversion and time-reversal symmetry breaking. Additionally, the presence of negative and asymmetric longitudinal magnetoresistance indicates anomalous velocity contribution to the magnetoresistance due to the Rashba–Dresselhaus spin–orbit interaction which is further studied by heat capacity.     

Spin hedgehog and collective magnetic quadrupole moments induced by parity and time invariance violating interaction

P- and T-odd interaction produces a spin distribution with the spins directed along the radius in spherically symmetric quantum systems. Due to the spin-dependent strong interaction this spin hedgehog contributes to P- and T-odd effects in neutron scattering, nuclear moments, etc. In deformed nuclei the P- and T-odd interaction produces a collective magnetic quadrupole moment. This moment induces P- and T -violating effects in atoms and molecules.     

Spin state transition in LaCoO3 studied using soft x-ray absorption spectroscopy and magnetic circular dichroism

Using soft x-ray absorption spectroscopy and magnetic circular dichroism at the Co-L(2,3) edge, we reveal that the spin state transition in LaCoO3 can be well described by a low-spin ground state and a triply degenerate high-spin first excited state. From the temperature dependence of the spectral line shapes, we find that LaCoO3 at finite temperatures is an inhomogeneous mixed-spin state system. It is crucial that the magnetic circular dichroism signal in the paramagnetic state carries a large orbital momentum. This directly shows that the currently accepted low- or intermediate-spin picture is at variance. Parameters derived from these spectroscopies fully explain existing magnetic susceptibility, electron spin resonance, and inelastic neutron data.