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neutron diffraction

This document discusses neutron diffraction and its applications. Neutron diffraction uses neutron scattering to determine the atomic and magnetic structure of materials. Neutrons can be scattered through both nuclear scattering via interaction with atomic nuclei, and magnetic scattering via interaction of the neutron's magnetic moment with the magnetic moments of atoms. This allows neutron diffraction to probe both atomic structure and magnetic ordering. Some key advantages of neutron diffraction are that neutrons are highly penetrating, non-destructive, and sensitive to light atoms. This technique is widely used to determine crystal and magnetic structures.

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NEUTRON DIFFRACTION Ashwani vishwakarma Roll no-290 M.Sc-II( inoganic chemistry)
Outline • Magnetic scattering • Neutron diffraction • Magnetic properties of neutron • Advantages and Disadvantages • Why neutron scattering is important • Application of Neutron diffraction
MAGNETIC SCATTERING • Neutron process a spin and associated magnetic moment , magnetic interaction between neutron and atomic electrons which is responsible for magnetic properties of moments may be expected . • Thus a neutron can be scattered by interaction of its magnetic moment with the atomic or ionic magnetic moment of the sample atom. • This type of scattering is generally referred to as magnetic scattering .
• Scattering diffracting of neutrons is caused by two effects. I. Nuclear scattering due to interaction of neutrons with atomic nuclei II. Magnetic scattering due to interaction of the magnetic moment of neutron with permagnet magnetic of atoms or ions.
• The magnetic moment of atoms in a paramagnetic crystal are arranged at random in the absence of external magnetic field hence magnetic scattering of neutron by such a crystal is also random.
NEUTRON DIFFRACTION • Neutron diffraction is the application of neutron scattering to the determination of the atomic /or magnetic structure of a material: A sample to be examined is placed in a beam of thermal, hot or cold neutrons to obtain a diffraction pattern that provides information of the structure ...
MAGNETIC PROPERTIES OF NEUTRON • The spin of an electron is approximately 1000 times larger than the magnetic moment of a neutron. • The magnetic moment of the neutron is sufficiently large to give rise to an interaction with unpaired electrons in magnetic atoms. • In compound containing elements of the first transition series in the periodic table (Iron, Cobalt and Nickel) the 3d shell contains unpaired electrons. • The magnetic field created by these unpaired electrons in the sample interact with the neutron magnetic moment to give magnetic scattering.
WHY NEUTRON SCATTERING IS IMPORTANT? Neutrons have No Charge! • Highly penetrating • Nondestructive • Can be used in extremes Neutrons have a Magnetic Moment! • Magnetic structure • Fluctuations • Magnetic materials Neutrons have Spin! • Polarized beams • Atomic orientation • Coherent and incoherent scattering Neutrons probe Nuclei! • Light atom sensitive • Sensitive to isotopic substitution
TYPES OF NEUTRON ELASTIC SCATTERING • no energy transfer to/from sample • crystal structure ,atomic correlation in liquid /glass INELASTIC SCATTERING • energy transfer to/from sample • Measurement of lattice vibration (phonons),atomic diffusion , molecular modes.
ADVANTAGES • Mass: Momentum transfer around interatomic distance • Zero charge: highly penetrating: measure bulk properties, can benefit from large samples, extreme sample environment (high/low temperature, magnetic field, pressure...) • Spin: polarization is possible • Magnetic dipole moment: Neutrons interact with unpaired electrons. Magnetic structure and spin excitations can be studied
DISADVANTAGES • Low brilliance of sources: low intensity or resolution, large samples, statistical noise. • Penetrating: background hard to control, need large samples • Some elements (B, Cd, Gd,..) strongly absorb • Neutral: hard to manipulate, accelerate, detect, etc
APPLICATION OF NEUTRON DIFFRACTION • Used for determination of structure • Locating Light atoms • Heavy atoms that absorb x-ray strongly • Similar atomic no /Isotopes • Magnetic properties • Single crystal studies analysis
Reference book’s • Spectroscopy by H . KUAR • Wikipedia
Thank you