Non-uniform thermal magnetization noise in thin films: application to GMR heads

A general scheme is developed to analyze the effect of non-uniform thermal magnetization fluctuations in a thin film. The normal mode formalism is utilized to calculate random magnetization fluctuations. The magnetization noise is proportional to the temperature and inversely proportional to the film volume. The total noise power is the sum of normal mode spectral noises and mainly determined by spin-wave standing modes with an odd number of oscillations. The effect rapidly decreases with increasing mode number. An exact analytical calcutaion is presented for a two-cell model.Comment: Paper for MMM'01, CB-10, to be published in J. Appl. Phy

Thermal stability of coupled ferromagnetic and superparamagnetic particles

We consider a single-domain ferromagnetic particle with uniaxial anisotropy coupled to a single-domain soft ferromagnetic particle (superparamagnetic particle). The problem of thermally agitated magnetization reversal in this case can be reduced to the random magnetization dynamics of the first particle with an effectively larger anisotropy field. The magnetic external field is also altered in a manner that depends on the sign of the coupling and can be either enhanced or suppressed.Comment: 3 pages, 2 figures, presented at MMM'0

Decay Properties Of The Dipole Isobaric Analog Resonances

A continuum-RPA-based approach is applied to describe the decay properties of isolated dipole isobaric analog resonances in nuclei having not-too-large neutron excess. Calculated for a few resonances in 90Zr the elastic E1-radiative width and partial proton widths for decay into one-hole states of 89Y are compared with available experimental data.Comment: 8 pages, 4 figures, prepared with RevTe

Impurity relaxation mechanism for dynamic magnetization reversal in a single domain grain

The interaction of coherent magnetization rotation with a system of two-level impurities is studied. Two different, but not contradictory mechanisms, the `slow-relaxing ion' and the `fast-relaxing ion' are utilized to derive a system of integro-differential equations for the magnetization. In the case that the impurity relaxation rate is much greater than the magnetization precession frequency, these equations can be written in the form of the Landau-Lifshitz equation with damping. Thus the damping parameter can be directly calculated from these microscopic impurity relaxation processes

Maximum thickness of a two-dimensional trapped Bose system

The trapped Bose system can be regarded as two-dimensional if the thermal fluctuation energy is less than the lowest energy in the perpendicular direction. Under this assumption, we derive an expression for the maximum thickness of an effective two-dimensional trapped Bose system.Comment: 1 pages, 0 figure

Metallic and insulating behaviour of the two-dimensional electron gas on a vicinal surface of Si MOSFETs

The resistance R of the 2DEG on the vicinal Si surface shows an unusual behaviour, which is very different from that in the (100) Si MOSFET where an unconventional metal to insulator transition has been reported. The crossover from the insulator with dR/dT0 occurs at a low resistance of R_{\Box}^c \sim 0.04h/e^2. At the low-temperature transition, which we attribute to the existence of a narrow impurity band at the interface, a distinct hysteresis in the resistance is detected. At higher temperatures, another change in the sign of dR/dT is seen and related to the crossover from the degenerate to non-degenerate 2DEG.Comment: 4 pages, 4 figure