On a Proposal for Determining the Thickness of the Transition Layer between Ferromagnetic Domains by a Neutron Polarization Experiment

Abstract

The surface energy of the Bloch wall between ferromagnetic domains is of fundamental importance in domain theory; this energy can be computed if the wall thickness is known. It is proposed that the wall thickness be measured by studying the polarization changes of a neutron beam which is passed through a single Bloch wall. The relation connecting wall thickness, neutron velocity, and polarization change is worked out; the required velocities are such that the experiment can probably be done with existing techniques, if grazing angles of incidence are used.

Numerical solution of Bloch's equation for neutron spin precession

“…The Runge-Kutta stepper routine, RK4BLOCH, is highly specialized and may be downloaded from the NISP web site [11]. Equations (10), (12), and (18)-(21) are coded explicitly; the only external function required is the one to compute B(t) along the trajectory. When BINTEGRAL is called from RK4BLOCH, the error parameter passed is ε /|γ |.…”

“…When the neutron emerges from the field, component P x will be 1 if the spin tracks the field rotation. The analytic expression for P x is [12] ( )…”

Structures magnétiques et polarimétrie neutronique

“…La grandeur du champ reste approximativement constante comme dans la Fig. A 2 En résolvant l'équation de Schrôdinger dépendant du temps ou l'équation "classique" dont nous venons de montrer qu'elle lui est équivalente, la polarisation finale a été calculée pour une rotation de % [25] ainsi que dans le cas général [26] Le comportement dynamique apparaît comme contrôlé par un seul "paramètre d'adiabaticité E", le rapport de la vitesse de précession de Larmor et de celle de rotation du champ de guidage (toutes deux peuvent être exprimés en deg/cm.). A l'extrême gauche de l'échelle d'adiabaticité, E est très petit, dans le repère du neutron le champ se réoriente rapidement, en moins de temps que la période de Précession de Larmor, le moment de spin du neutron reste dans la direction initiale.…”

On the Scattering of Neutron in the Magnetic Field οf 180° Bloch Wall

“…Calculating, for example, transmittance coefficients for some or other wall magnetization law as functions of δ, one can evaluate the real value of δ for this ferromagnetic material, fitting those calculated values to measured transmittance data [2]. The elementary calculations were presented in [3] where the neutron was considered as a classical particle whose magnetic moment vector precesses under the influence of the DW magnetic field. In a classical approximation they can derive only transmittance coefficients for neutron with and without flip, its sum is equal to one, whereas the reflection phenomena are ignored.…”

“…In this work the authors, similarly as in [3], used the one-helix approximation of the wall magnetization law. By this, the magnetization vector M rotates harmonically between two parallel planes which form an imaginary slab and M is considered as a permanent vector out of this slab.…”