摘要:

A survey is given of some current applications of neutron diffraction to the elucidation of a wide range of the properties of both magnetic and non-magnetic materials. Naturally, one must use quantum mechanics in obtaining the details necessary for the interpretation of experimental results, though some useful semiclassical visualization is possible. The analysis of the dynamics of atomic systems into elementary, nearly independent excitations started with Debye's analysis of vibrational modes in 1912, and this gave rise to the quantized unit of vibrational energy, the phonon. Likewise, magnetic spin-wave theory started with Bloch in 1932 and in its quantized form gives us the ‘magnon’ concept. In complex structures, in liquids, and near the critical point theoretical concepts are less clear and we may use the neutron experiments to help us decide on the most appropriate approximation to use in describing them. We now seem to have a tool of remarkable power to help in solving the complex problems of energy levels and the dynamics of crystals.

ISSN:0010-7514    

DOI:10.1080/00107516608205483

出版商:Taylor & Francis Group    

年代:1966

数据来源: Taylor

摘要:

In this article we examine the available evidence concerning the existence of magnetic charge. We find that the experimental evidence against it is very strong. We also find that its discovery would cause considerable difficulty in conventional theoretical physics, but that no conclusive theoretical argument against its existence has yet been found. The apparent absence of magnetic charge in nature remains unexplained and rather disquieting.

ISSN:0010-7514    

DOI:10.1080/00107516608205484

出版商:Taylor & Francis Group    

年代:1966

数据来源: Taylor

摘要:

A description is given of the transient variation of the earth's magnetic field known as the quiet day variation field and theSqandLionospheric dynamo current systems which can be inferred from its characteristics. Sounding rocket investigations of the magnetic field discontinuities obtained when this current system is penetrated are reviewed and the need to measure other dynamo parameters is discussed.

ISSN:0010-7514    

DOI:10.1080/00107516608205485

出版商:Taylor & Francis Group    

年代:1966

数据来源: Taylor

摘要:

Formulae for the radiation pressure of electromagnetic and of sound waves are reviewed. The pressure on an obstacle in the path of the waves can be calculated from the momenta of the incident and scattered trains, and it is now well established that any train of waves of intensityJpropagated with speedvhas momentumJ/v2per unit volume. A general proof of this result is proposed, independent of the nature of the waves.

ISSN:0010-7514    

DOI:10.1080/00107516608205486

出版商:Taylor & Francis Group    

年代:1966

数据来源: Taylor

摘要:

In this paper it is shown how a discussion of processes slow enough to be considered adiabatic in the thermodynamic sense can be used in such widely different fields as radiation theory, quantum theory, theory of electrolytes and plasma physics to obtain relations which have a general validity.

ISSN:0010-7514    

DOI:10.1080/00107516608205487

出版商:Taylor & Francis Group    

年代:1966

数据来源: Taylor

摘要:

There has been growing interest in recent years in the intrinsic stresses in evaporated thin films. Apart from the relevance of such stresses to nucleation theory, film structure and gas absorption, their measurement and control is of importance in many thin film optical components. In some cases, the stresses can lead to the complete breakdown of thin films resulting in optical scattering and occasionally substrate deformation.

ISSN:0010-7514    

DOI:10.1080/00107516608205488

出版商:Taylor & Francis Group    

年代:1966

数据来源: Taylor

摘要:

A logical sequence of ideas in electromagnetism can be based on the behaviour of a current-carrying coil as a magnetic dipole of moment μiA, where μ is the permeability of the medium in which the coil is situated, i the current and A the effective area (area × number of turns) of the coil (Chalmers 1965). The occurrence of μ rather than μois verified from the effect of permeability on self-inductance.

ISSN:0010-7514    

DOI:10.1080/00107516608205489

出版商:Taylor & Francis Group    

年代:1966

数据来源: Taylor

摘要:

How to Find Out about Physics. By B. Yates. (Pergamon Press, 1965.) [Pp. x+175.] 15s.

ISSN:0010-7514    

DOI:10.1080/00107516608205490

出版商:Taylor & Francis Group    

年代:1966

数据来源: Taylor