Magnetic scattering

The general cross section for the scattering of neutrons by magnetic interactions, derived from the master formula [Eq. (3.4)] and the interaction potential between a neutron and an electron with spin and momentum is derived by Marshall and 

Lovesey (1). We are interested in elastic scattering from spin-only systems where, for discussing magnetic scattering at low x at least, residual orbital effects introduced via spin-orbit coupling may be accounted for by a factor g/2 associated with the form factor, where the g-factor may be determined by magnetic resonance measurements. 

Paramagnets. In the absence of magnetic fields, there is no coherent scattering from paramagnets because of the random orientation of the magnetic ions. The differential cross section is 

In a magnetic field at low temperatures a paramagnet will be significantly polarized in an applied field of several kgauss. The cross section is then 

Magnetically Ordered Systems. For magnetically ordered systems the discussion is analogous to that for nuclear scattering. By comparison with (3.15) the magnetic Bragg cross section is 

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Table 1. Separation of spin and orbital moments from magnetic scattering and magnetization measurement in USe and UTe compounds (in bohr magneton unit).

The interaction Hamiltonian contains the operator A, corresponding to the vector potential A of the electromagnetic field.2 Excluding magnetic scattering, the interaction Hamiltonian is given by... 

Diffuse magnetic scattering just above the ordering temperature allows study of spatial correlations. Such measurements on confirmed ideas about anisotropic... 

X-ray resonant magnetic scattering measurements of the Ni and F signals have verified that the coupled CuNi and Py layers switch in tandem and that the switching of the pinned and free CuNi/Py layers are well separated J. W. Freeland (unpublished). 

An important modern tool for the direct observation of spin configurations is neutron diffraction. Because the neutron is a neutral particle that carries a magnetic moment, it is primarily scattered by only the atomic nucleus and electrons with unpaired spins. Halpern and Johnson (247) have shown that the differential scattering cross section of an atom, including both nuclear and magnetic scattering, is... 

The treatment presented here could be extended to address magnetic materials as well. For the sake of completeness and as an illustration, the magnetic scattering of a neutron beam (unpolarized) can be written equivalently to equation 4 presented earlier as ... 

Extensively used to locate hydrogen atoms. May ve additional information due to spin ) on neutron leading lo magnetic scattering... 

The theory of the magnetic scattering of thermal neutrons has been described in some detail by Marshall and Lovesey (1). Only a brief outline of those relations relevant to the present discussion will be given here. This limits the discussion to elastic scattering by spin-only systems ). Experimental techniques such as time-of-flight diffractometery are not discussed as no applications have yet been made to the subject under discussion. 

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