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Clifford Shull and J. Samuel Smart used neutron diffraction to detect antiferromagnetism. Oppositely oriented magnetic sublattices can have no net bulk magnetization, yet their spatial order produces a distinct scattering pattern because neutrons interact with magnetic moments. The experiment therefore probes internal magnetic arrangement, not just the total magnetic moment of a sample. It established neutron scattering as a way to reveal ordered magnetism that bulk magnetic measurements can conceal.^[ref]

A physicist who developed neutron scattering experiments and became a professor of physics at MIT.^[ref]

A physicist who used neutron scattering to investigate lattice dynamics, including the phonon anomaly associated with the Peierls transition in TTF-TCNQ.^[ref]

Memorial biography: ieee-uffc.org/contact/gen-shirane

A physicist whose neutron scattering research investigated condensed matter, including solid buckminsterfullerene. Neutrons provide structural information that complements a material’s bulk properties. He also developed an exposition of neutron diffraction from powdered samples for students and other nonspecialists, making the connection between measured scattering patterns and material structure more accessible.^[ref]

A Kiessig fringe is an oscillation in reflected intensity caused by wave interference between contributions from the two sides of a thin film. For specular neutron scattering at grazing angle $\theta$ and wavelength $\lambda$, the normal wave vector transfer is $q_z=4\pi \sin \theta /\lambda$. Well above the critical edge, a film of thickness $d$ contributes a relative wave phase approximately $q_{z}d$, giving fringe spacingThus closely spaced fringes indicate a thicker film. As a calculated example, spacing $0.0628\mathrm{n}{\mathrm{m}}^{-1}$ corresponds to about $100\mathrm{nm}$. Interface surface roughness, contrast, additional layers and instrumental resolution affect the fringe pattern; thickness is inferred with an appropriate reflectivity model, especially near the critical edge.^[ref]

Neutron scattering measures how a specimen changes the directions and kinetic energies of incident neutrons. Neutron diffraction uses the elastic scattering pattern to investigate crystal structure and magnetic order; inelastic neutron scattering uses energy transfer to investigate excitations such as phonons and magnons. The two measurements ask complementary questions: what arrangement repeats in space, and what disturbances can propagate through it?

The 1994 Nobel Prize in Physics recognized Clifford Glenwood Shull's diffraction work and Bertram Neville Brockhouse's spectroscopy.^[ref]

Nuclear scattering couples to atomic nuclei; magnetic scattering couples the neutron's magnetic moment to electronic magnetic moments. The latter underlies both magnetic neutron diffraction and magnon spectroscopy. An atomic number is not a nuclear neutron scattering weight: the relevant coefficient in the elementary coherent model is the nuclear neutron scattering length.

For pioneering neutron scattering techniques for studying condensed matter, Bertram Neville Brockhouse received one half for developing neutron spectroscopy, while Clifford Glenwood Shull received one half for developing neutron diffraction.^[ref]

An experimental physicist who developed low-temperature apparatus and studied atoms and molecules adsorbed on surfaces. At Washington he built a dilution refrigerator operating down to about 0.015 K, enabling measurements of thin helium, hydrogen and oxygen films. Combining thermodynamic measurements with neutron scattering helps reveal how confinement to a surface changes the behavior of matter.^[ref]

Determining antiferromagnetic magnetic order is a good reason to use neutron scattering. The neutron has a magnetic dipole moment, so its scattering amplitude includes the spatial arrangement of electronic magnetic moments. Alternating magnetic moments can produce magnetic neutron diffraction peaks even when there is no change of the nuclear crystal structure. Ordinary nonresonant X-ray diffraction primarily measures the electron density, and is much less sensitive to this magnetic order.

Assume a homogeneous Fe–Cr–Ni alloy, normal incidence, independent scattering events and the stated effective scattering cross-sections. Neglect absorption, other constituents and changes in neutron energy within the thin sheet. The atomic fractions are not supplied; take $x_{\mathrm{Fe}}=0.70$, $x_{\mathrm{Cr}}=0.20$, $x_{\mathrm{Ni}}=0.10$ as an explicit representative assumption, not a composition measured or specified in the paper.

The conventional cell of a face-centered cubic lattice containsatoms. The number density is thereforeFor a mixture, the scattering probability per unit path length is ${\Sigma }_s={\sum }_j{n}_j{\sigma }_j=n{\bar{\sigma }}_s$, whereThus ${\Sigma }_s=27.751{\mathrm{m}}^{-1}$. For thickness $t=10^{-3}\mathrm{m}$, the unscattered fraction $U$ satisfies $dU/dz=-{\Sigma }_{s}U$ with $U(0)=1$. The fraction undergoing at least one neutron scattering event isThe thin-sheet approximation gives $P_s\simeq {\Sigma }_{s}t=2.78\%$, consistent to the accuracy of the assumed composition. A simple iron-dominated estimate ${\bar{\sigma }}_s\simeq 3.2$ barns gives essentially the same about $3\%$ scattered conclusion.

For any other assumed composition, use the displayed weighted formula; mass fractions must first be converted to atomic fractions. Since the supplied elemental cross-sections span $2.8$–$4.1$ barns, any mixture of these three elements at the stated number density gives approximately $2.39$–$3.48\%$. This is a bound within the idealized mixture model, not a claim that every such composition is stable austenite.