Role of domain wall fluctuations in non-Fermi liquid behavior of metamagnets

We study resistivity temperature dependence of a three dimensional metamagnet near the metamagnet phase transition point in the case when magnetic structure tends to split into regions with high and low magnetization. We show that in the case of weak pinning the spin relaxation time of domain wall is much larger than that of the volume spin fluctuations. This opens a temperature range where resistivity temperature dependence is determined by scattering of conducting electrons by the domain wall fluctuations. We show that it leads to quasi-linear low temperature dependence of resistivity

Magnetocaloric effect and magnetization in a Ni-Mn-Ga Heusler alloy in the vicinity of magnetostructural transition

The magnetic and thermodynamic properties of a Ni2.19Mn0.81Ga alloy with coupled magnetic and structural (martensitic) phase transitions were studied experimentally and theoretically. The magnetocaloric effect was measured by a direct method in magnetic fields 0-26 kOe at temperatures close to the magnetostructural transition temperature. For theoretical description of the alloy properties near the magnetostructural transition a statistical model is suggested, that takes into account the coexistence of martensite and austenite domains in the vicinity of martensite transformation point.Comment: presented at ICM-2003, to appear in JMM

Magnetic properties of Ni2.18Mn0.82Ga Heusler alloys with a coupled magnetostructural transition

Polycrystalline Ni2.18Mn0.82Ga Heusler alloys with a coupled magnetostructural transition are studied by differential scanning calorimetry, magnetic and resistivity measurements. Coupling of the magnetic and structural subsystems results in unusual magnetic features of the alloy. These uncommon magnetic properties of Ni2.18Mn0.82Ga are attributed to the first-order structural transition from a tetragonal ferromagnetic to a cubic paramagnetic phase.Comment: 4 pages, 4 figures, revtex

Spatio-Temporal Stochastic Resonance of Domain Walls in Inhomogeneous Magnets

. We study the motion of a small-angle domain wall (DW) in a rhombic ferromagnet with localized attracting inhomogeneities in the vicinity of the reorientational phase transiton induced by temperature. Usually a DW can be trapped by the inhomogeneities. If the system is additionally driven by a noisy magnetic field the DW is able to perform stochastic motion and hence achieves probability to jump between several attracting inhomogeneities. With a small periodic field applied to the system we will observe stochastic resonance in the motion of the DW. At an optimal noise level the hopping dynamics of the DW become most coherent and the response of the system to the periodic force is maximal. 1. Introduction In the last decade the phenomenon of stochastic resonance (SR) has attracted much attention. This phenomenon underlies a "positive", constructive role which noise might play in nonlinear systems: with an increase of noise applied to a nonlinear system a response of the system to a s..

Stochastic resonance in ferromagnetic domain motion

A model for the motion of a single ferromagnetic domain is studied numerically and analytically. A single strip in two dimensions and pinned at two inhomogeneities is considered. We suppose two stable configurations (positively or negatively curved with pinned ends) due to the action of a bistable potential. Further, it is assumed that the domain is driven externally by periodic and noisy magnetic fields. The noise makes the domain able to flip between the two configurations. The small temporally periodic fields synchronize these flippings and the phenomenon of stochastic resonance is observed. The signal to noise ratio of the output is investigated and shows a maximum for a nonvanishing intensity of the applied noise. Its dependency on the stiffness of the domain is studied