Search

Our experimental measurements for the magnetization M as a function of temperature are analyzed for the multilayer structure of CoMnFeGe for x = 0.085 and x = 0.12 at constant magnetic fields of 3, 5, and 7 T. For this analysis, a power-law formula is used below the transition temperature T for these compositions and the values of the critical exponent β for the magnetization M (order parameter) are determined. Our analysis indicates that a first order transition at lower concentrations ( x = 0.085) changes toward a second order at higher concentrations ( x = 0.12) at constant magnetic fields (3, 5, and 7 T) for the multilayer CoMnFeGe, as observed experimentally. [ABSTRACT FROM AUTHOR]

Temperature dependences of the magnetization (ferromagnetic) and the staggered magnetization (antiferromagnetic) are analyzed for various ferromagnetic (FM) and antiferromagnetic (AF) phases of the layered structure of La 0.6 Nd 0.4 Mn 2 Si 2 using the experimental data at a constant magnetic field of 50 Oe. For this analysis, a mean field model with the quadratic coupling between the magnetization (FM) and the staggered magnetization (AF) is considered and the expressions derived from the mean field model for the magnetization and the staggered magnetization, are fitted to the experimental data. Our results indicate that the quadrupole–quadrupole interactions for the ferromagnetic and antiferromagnetic spin configurations play a dominant role to describe the ferromagnetic and antiferromagnetic properties of the layered structure of La 0.6 Nd 0.4 Mn 2 Si 2 . [ABSTRACT FROM AUTHOR]

Abstract: The influences of iron-alloying on the structure, magnetic and magnetocaloric properties of the Tb5Si2Ge2 compound have been studied using X-ray powder diffraction and magnetization measurements. X-ray diffraction studies show that both the alloyed and non-alloyed samples crystallize in the P1121/a monoclinic structure at room temperature. As the temperature is lowered, a first-order magnetic transition is observed in the parent compound, whereas only a second-order magnetic transition is recorded for the compounds alloyed with iron. Iron-alloying in small amounts of 2x ≈0.05 reduces the magnetic hysteresis significantly while retaining the magnitude of the change in magnetic entropy change. [Copyright &y& Elsevier]

Experimental measurements for the magnetization at various temperatures are analyzed using a mean field model for the purely ferromagnetic spin configuration near the metamagnetic phase transitions in LaNdMnSi ( x=0.3) at a constant magnetic field (50 mT). By fitting the temperature dependence of the magnetization from the free energy in the mean field model to the experimental data for this compound, the coefficients in the free energy expansion are determined. Our analysis of the magnetization describes a first-order character of the metamagnetic transition in LaNdMnSi ( x=0) on the basis of the mean field model studied here. [ABSTRACT FROM AUTHOR]

The magnetic field–temperature ( H – T ) phase diagram is calculated using the mean field theory by expanding the free energy in terms of the uniform and staggered magnetization for the ferromagnetic–antiferromagnetic transitions in the La 0.6 Nd 0.4 Mn 2 Si 2 multilayer structures. Using our experimental measurements, analysis of the magnetization as a function of the magnetic field at constant temperatures from 45 K to 250 K is performed by a power-law formula close to the ferromagnetic–antiferromagnetic transitions. Also, by obtaining the magnetic field dependence of the isothermal susceptibility χ T from the M – H curves, χ T vs. H − H c is analyzed ( H c is the critical magnetic field) using a power-law formula for the antiferromagnetic–ferromagnetic (AF–FM) transitions in La 0.6 Nd 0.4 Mn 2 Si 2 . It is found that a discontinuous (first order) transition which occurs at the lowest (45 K) and the highest (250 K) temperatures, changes to a continuous one at a constant temperature at around 100 K as the magnetic field carries the systems from the antiferromagnetic to the ferromagnetic phase. Values of the critical exponents associated with this transition are deduced and they are compared with the predictions of some theoretical models. [ABSTRACT FROM AUTHOR]