Showing papers on "Metamagnetism published in 1980"

Itinerant metamagnetism in TiBe2

Abstract: The high field magnetization data of Monod, Felner, Chouteau and Shaltiel [1] on TiBe2 are discussed in terms of a metamagnetic transition in fields about 5 T.

Magnetic properties of cerium monotelluride

Abstract: 2014 Magnetization, magnetic susceptibility and neutron scattering measurements have been performed on CeTe single crystals, in order to study the low temperature magnetic properties. We observe at T 2 K a metamagnetic transition for a magnetic field of about 18 kOe, associated with an hysteresis cycle. By neutron scattering measurements we determine a magnetic moment 03BC = 0.2 ± 0.1 03BCB/Ce surprisingly low and different from the value deduced from the high field magnetization measurements. J. Physique 41 (1980) 1117-1120 OC TOBRE 1980,

Theory of collinear metamagnetism II: High density expansion method☆

Abstract: A special case of the spin system proposed in the previous paper (i.e., paper I of the same series) is considered, which includes only the Ising term besides the four-spin coupling. In view to describe adequately collinear metamagnets, the thermodynamic properties of this model are investigated. The high density expansion method is used to this purpose, in the approximation including Gaussian fluctuations of the molecular field. A new way is shown for calculating the mean square of molecular field fluctuations. Free energy, magnetization, phase diagram as well as mean squares of fluctuations are calculated for metamagnets. Our results agree satisfactorily with experimental data for Mn 3 GaC.

Theory of collinear metamagnetism I: Unified treatment of field- and temperature-induced metamagnets☆

Abstract: A two-sublattice spin model is proposed with special four-spin interactions besides the usual exchange terms. The four-spin interaction terms are assumed not to be the even functions of the spin sublattice operators. Thermodynamical properties of this model are investigated in the molecular field approximation. The complete phase diagrams for all experimentally discovered collinear two-sublattice metamagnets are obtained numerically. Moreover some unknown kinds of phase diagrams are found, determining the new types of metamagnets which have not been experimentally observed so far. Finally, the theoretical results fitted for the FeCl2 and Mn3GaC, are compared with experiment.

Optical Investigations of YbCrO 3 . II. Metamagnetic Transition in YbCrO 3

Abstract: R exciton lines of YbCrO 3 corresponding to the 4 A 2 g → 2 E g transition of Cr 3+ have been measured at 4.2 K, where a first order phase transition induced by magnetic field H 0 (// a )∼67 kOe has been found. We concluded that this phase transition is a metamagnetic transition at which ths weak ferromagnetic moment of the Cr 3+ spins reverses its coupling with the magnetic moment of the Yb 3+ spins from antiparallel to parallel. By the analysis of the spectral changes in the metamagnetic transition, the molecular field upon the Cr 3+ ion due to the Cr–Yb magnetic interaction was estimated. Generally, if the mnagnetic moment of the rare-earth spins couples antiparallel to the weak ferromagnetic moment of the transition-metal spins for other orthochromites and orthoferrites, the metamagnetic transition of this type will be expected.

Theory of collinear metamagnetism III: Magnons spectrum by renormalized high density expansion☆

Abstract: A special case of the spin system proposed in the previous paper (i.e. the first paper of this series) is considered, which includes the Heisenberg term besides the four-spin coupling. By means of an improved renormalization within the high density expansion method, the formulas for the temperature-dependent spectra of magnons are obtained, which comprise the whole influence of Gaussian fluctuations of the molecular field. In the whole range of temperature and magnetic field considered the magnon energies are calculated and their jumps at the metamagnetic transition points are established. Existence limits of particular phases are obtained which consequently give the maximum width of a hysteresis loop. A highly interesting thermodynamic phase diagram of the FeBr2 type is derived from our model. The extraordinary behaviour of FeBr2 turns out to follow from the presence of the four-ion term in our model.

The new metamagnetic Eu5Sn3S12

Abstract: The heat capacity (C), magnetic susceptibility (χ), and magnetization (M) of Eu5Sn3S12 are investigated. C is measured by a vacuum adiabatic calorimeter (T = 2 to 300 K). Three anomalies are found in the C(T) dependence: two maxima at 4 and 7K and a bend at 3K. The thermodynamic functions S2 to 298.15 K = 724 J/mol K and H2 to 298.15 K = 97.70 kJ/mol are calculated. Magnetic properties are investigated by a vibrating sample magnetometer in fields up to 30 kOe in the temperature range 1.7 to 200 K. The existence of two field-dependent antiferromagnetic phases in Eu5Sn3S12 are found at low temperatures (< 7 K). 1/χ(T) is linear above 35 K (CM = 27, θp = −2.5 K). The M(H) behaviour is of step character inherent to metamagnetism. [Russian Text Ignored].

Classical Theory of a Metamagnet with Temperature‐Dependent Anisotropy

Abstract: The collinear, two-sublattice metamagnet with thermal dependence of the magnetic anisotropy parameter but with constant parameter of the inter-sublattice isotropic exchange coupling is investigated in classical approximation. Using Pal's form of the phenomenological free energy, the magnetization curves for both mT(h) and mh(T) processes are derived. The possibility of occurrence of the spontaneous metamagnetism is demonstrated and its criterion is derived. Moreover, the stable oblique phase is studied, exhibiting new interesting abrupt magnetic transitions on its phase boundaries. Some rules for the accompanying volume jumps are established. [Russian Text Ignored.]