Magnetic Properties Of Spin-1 Research Articles

Possible ferromagnetism of dense quark matter

The cardinal focus of the present review is to investigate the possibility of the para-ferro phase transition of dense quark matter. For these, the calculation of the single-particle energies, ground state energy (GSE) densities, and spin susceptibility χ of degenerate quark matter with one gluon exchange interaction in terms of spin-dependent Landau parameters (LPs) have been presented. The expressions for the GSE and χ of cold and dense spin-polarized quark matter have been derived with corrections due to correlation. Furthermore, the magnetic properties of spin polarized quark matter have been discussed by evaluating the magnetization ⟨M⟩ and magnetic susceptibility χM in terms of LPs. Finally, the possibility of magnetic instability has been revealed by studying the density dependence of ⟨M⟩ and χM.

Growth and magnetic properties of spin coated Co0.6Zn0.4Mn0.3Fe1.7O4 ultrathin films on silicon (100), (110) and (111) substrates

This paper reports growth of Co0.6Zn0.4Mn0.3Fe1.7O4 (CZFMO) ultrathin films (thickness: 23–30 nm) by spin coating technique on silicon (100), (110) and (111) substrates. The deposited films were annealed at 700 °C for 1 h in the oxygen environment. All the films were found to be polycrystalline in nature. The CZFMO films were found to have minimal residual stress (13–50 MPa), which could be an encouraging feature for novel microwave miniaturized device applications. Room temperature magnetic measurements demonstrated completely saturated hysteresis loop with the highest squareness ratio (M R /M S ) ~ 60% for the film grown on Si (110) substrate. On the other hand CZFMO films on Si (100) and Si (111) substrates showed unsaturated hysteresis loops with M R /M S ~ 10 and 5%, respectively. The reason for the better magnetic properties of the ultrathin CZFMO film on Si (110) substrate seems to be its better crystalline quality and larger grain size compared to those of other films.

Structural and magnetic properties of spin-1/2 dimer compound Cu2(IPA)2(DMF)(H2O) with a large spin gap

We present the synthesis and a detailed investigation of structural and magnetic properties of metal-organic compound Cu2(IPA)2(DMF)(H2O) by means of x-ray diffraction, magnetization, and heat capacity measurements. Single crystals of the title compound were synthesized by judicious selection of organic ligand and employing a selective hydrothermal reaction route. It crystallizes in an orthorhombic structure with space group Cmca. The structural analysis revealed that two Cu2+ ions are held together by the organic component (-O-C-O-) in a square paddle-wheel to form spin dimers which are aligned perpendicular to each other and are further coupled through organic ligands (isophthalic acid) forming two-dimensional layers. Temperature dependent magnetic susceptibility could be described well using spin-1/2 dimer model. The spin susceptibility shows an exponential decrease in the low temperature region, below the broad maximum, confirming the singlet ground state with a large spin gap of K. The heat capacity Cp measured as a function of temperature also confirms the absence of magnetic long-range-order down to 2 K.

Magnetic properties of spin-1/2 Fermi gases with ferromagnetic interaction

We investigate the magnetic properties of spin-$1/2$ charged Fermi gases with ferromagnetic coupling via mean-field theory, and find the interplay among the paramagnetism, diamagnetism and ferromagnetism. Paramagnetism and diamagnetism compete with each other. When increasing the ferromagnetic coupling the spontaneous magnetization occurs in a weak magnetic field. The critical ferromagnetic coupling constant of the paramagnetic phase to ferromagnetic phase transition increases linearly with the temperature. Both the paramagnetism and diamagnetism increase when the magnetic field increases. It reveals the magnetization density $\bar M$ increases firstly as the temperature increases, and then reaches a maximum. Finally the magnetization density $\bar M$ decreases smoothly in the high temperature region. The domed shape of the magnetization density $\bar M$ variation is different from the behavior of Bose gas with ferromagnetic coupling. We also find the curve of susceptibility follows the Curie-Weiss law, and for a given temperature the susceptibility is directly proportional to the Land\'{e} factor.

Quantum phase transition and magnetic plateau in three-leg antiferromagnetic Heisenberg spin ladder with unequal J1–J2–J1 legs

Magnetic properties of spin-1/2 antiferromagnetic three-leg Heisenberg ladders, where antiferromagnetic interactions in legs are J1, J2 and J1 respectively and in the rungs are J⊥, have been investigated by bond-mean field method. As J⊥ changes, magnetization curves show different behavior. For J⊥=0.5, there are cusps in magnetization curves, while for J⊥=3.0, the 1/3 magnetization plateau appears, which can be explained by energy spectra. Furthermore, for J⊥=3.0 the 1/3 magnetization plateaus will become wider or narrow down with J2 changing. In addition, the mean-field bond parameters and the concurrences, which confirm the phase transitions, are also studied.

INTERNAL ENERGY OF HEISENBERG SPIN-1/2 J1 - J2 ANTIFERROMAGNET ON THE BODY-CENTERED-CUBIC LATTICE IN TYABLIKOV APPROXIMATION

Magnetic properties of spin ½ J 1 - J 2 quantum Heisenberg antiferromagnet on body centered cubic lattice are investigated in the paper. By using two-time temperature Green's functions, sublattice magnetization and critical temperature depending on the frustration ratio J 2 / J 1 are obtained in both stripe and Neel phase. The analysis of ground state sublattice magnetization and internal energy indicates the first order phase transition from Neel to stripe phase for 0.7< J 2 / J 1 < 0.8, which is in agreement with previous studies.

INTERNAL ENERGY OF HEISENBERG SPIN-1/2 J1 - J2 ANTIFERROMAGNET ON THE BODY-CENTERED-CUBIC LATTICE IN TYABLIKOV APPROXIMATION

Magnetic properties of spin ½ J1-J2 quantum Heisenberg antiferromagnet on body centered cubic lattice are investigated in the paper. By using two-time temperature Green's functions, sublattice magnetization and critical temperature depending on the frustration ratio J2/ J1 are obtained in both stripe and Neel phase. The analysis of ground state sublattice magnetization and internal energy indicates the first order phase transition from Neel to stripe phase for 0.7 J2/ J1 0.8, which is in agreement with previous studies.

Single-ion anisotropy, Dzyaloshinskii-Moriya interaction, and negative magnetoresistance of the spin-12pyrochloreR2V2O7

The electronic and magnetic properties of spin-1/2 pyrochlores R2V2O7 were investigated on the basis of density-functional calculations. Contrary to the common belief, the spin-1/2 V4+ ions are found to have a substantial easy-axis single-ion anisotropy. The |D/J| ratio deduced from the magnon quantum Hall effect of Lu2V2O7, where J is the nearest-neighbor spin exchange and D is the Dzyaloshinskii-Moriya parameter, is much greater than the value estimated from our calculations (i.e., 0.32 vs. 0.05). We show that this discrepancy is due to the neglect of the single-ion anisotropy of the V4+ ions, and the negative magnetoresistance observed for R2V2O7 arises from a new mechanism.

Magnetic Properties of Spin- and Charge-doped Sr0.7La0.3Ti0.9Co0.1O3

Magnetic Properties of Spin- and Charge-doped Sr0.7La0.3Ti0.9Co0.1O3

The magnetic properties of spin-1/2 and spin-1 Ising models in an applied magnetic field by introducing the effective-field approximation

A method in Ising models is presented within the framework of the effective-field theory (EFT) with correlations. In the present method, we have improved the EFT method by including the correlations between the different spins which emerge when expanding the identities. To do this, we have derived a set of linear equations for the considered system by taking as a basis the thermal averages of a central spin and a perimeter spin at the site i, which is defined within spin identities and differential operator technique. By solving numerically the set of linear equations derived for the Ising system with coordination number q=3, we have evaluated numerically all spin correlation functions without using a kind of decoupling approximation in the spin system under a longitudinal magnetic field. The effects of the longitudinal magnetic field on magnetic properties of the spin systems are discussed in detail. Numerical results are performed and analyzed for the cases of spin-1/2 in a longitudinal magnetic field and spin-1 with crystal field in a longitudinal magnetic field, respectively on the honeycomb lattice. A number of interesting phenomena, originating from the external field and temperature have been found.

Structural and magnetic properties of spin- and charge-doped Sr0.8La0.2Ti0.9Co0.1O3

The structural and the magnetic properties of spin- and charge-doped Sr0.8La0.2Ti0.9Co0.1O3 have been investigated. The sample shows a cubic structure at room temperature. The temperature dependence of magnetization (M) of Sr0.8La0.2Ti0.9Co0.1O3, in both zero-field-cooled (ZFC) and field-cooled (FC) modes between 100 and 70000Oe, was measured. It is found that the sample undergoes the paramagnetic-ferrimagnetic phase transition at around 50K, and the MZFC curve lies above the MFC one below 32K when the applied field is less than 2000Oe. This unusual behavior can be understood as a superposition of ferrimagnetic and paramagnetic contributions to the magnetization.

Magnetic Properties of Spin-1/2 IsingSuperlattice

Using the effective-field theorywe studied the magnetic properties of aspin-1/2 Ising superlattice, which consist of three different ferromagnetmaterials. The magnetic behavior of this superlattice is examined. Thecritical temperature and the compensation temprature of the system arestudied as a function of the exchange interactions between thenearest-neiboring spins across the interface and in the intraface.Temperature dependence of magenetizations is also given.

Coherent-Potential Approximation for Disordered Ferromagnetic Binary Alloys

The magnetic properties of spin-\textonehalf{} Heisenberg ferromagnetic alloys are calculated. We calculate the spin-wave Green's function in the random-phase approximation and treat the disordered composition-dependent exchange interaction in a coherent-potential approximation (CPA). In the weak-scattering limit, the CPA reproduces the result of the mean-field theory as expected, and in the strong-scattering limit, the CPA predicts such properties as critical concentration, which is beyond the scope of the mean-field theory.