A pr 2 00 5 Magnetism and the Weiss Exchange Field-A Theoretical Analysis Inspired by Recent Experiments

The huge spin precession frequency observed in recent experiments with spin-polarized beams of hot electrons shot through magnetized films is interpreted as being caused by Zeeman coupling of the electron spins to the so-called Weiss exchange field in the film. A “Stern-Gerlach experiment” for electrons moving through an inhomogeneous exchange field is proposed. The microscopic origin of exchange interactions and of large mean exchange fields, leading to different types of magnetic order, is elucidated. A microscopic derivation of the equations of motion of the Weiss exchange field is presented. Novel proofs of the existence of phase transitions in quantum XY -models and antiferromagnets, based on an analysis of the statistical distribution of the exchange field, are outlined.

[1]  Ute Dreher,et al.  Statistical Mechanics Rigorous Results , 2016 .

[2]  J. Froehlich,et al.  Hund’s Rule and Metallic Ferromagnetism , 2004, cond-mat/0404483.

[3]  J. Fröhlich,et al.  Another Return of “Return to Equilibrium” , 2004, math-ph/0410011.

[4]  Vojkan Jaksic,et al.  Perturbation Theory of W*-Dynamics, Liouvilleans and KMS-States , 2003 .

[5]  H. Tasaki.  Ferromagnetism in the Hubbard Model: A Constructive Approach , 2003, cond-mat/0301071.

[6]  J. Froehlich,et al.  KMS, etc , 2002, math-ph/0204023.

[7]  W. Weber,et al.  Magnetization Precession by Hot Spin Injection , 2001, Science.

[8]  J. Fröhlich,et al.  Return to equilibrium , 2000 .

[9]  W. Weber,et al.  The ferromagnetic spin filter , 1999, IEEE International Magnetics Conference.

[10]  N. Datta,et al.  Effective Hamiltonians and Phase Diagrams for Tight-Binding Models , 1998, math-ph/9809007.

[11]  J. Froehlich,et al.  Renormalization Group Methods: Landau-Fermi Liquid and BCS Superconductor , 1995, cond-mat/9508063.

[12]  E. Thiran,et al.  Quantum Theory of Large Systems of Non-Relativistic Matter , 1995, cond-mat/9508062.

[13]  H. Leutwyler,et al.  Nonrelativistic effective Lagrangians. , 1993, Physical review. D, Particles and fields.

[14]  H. Tasaki,et al.  Ferromagnetism in the Hubbard model , 1993, cond-mat/9305026.

[15]  E. Fradkin,et al.  Field theories of condensed matter systems , 1991 .

[16]  E. Lieb,et al.  Phase transitions in quantum spin systems with isotropic and nonisotropic interactions , 1978 .

[17]  E. Lieb,et al.  Phase Transitions and Reflection Positivity . I . General Theory and Long Range Lattice Models , 1978 .

[18]  J. Fröhlich,et al.  Phase Transitions in Statistical Mechanics and Quantum Field Theory , 1977 .

[19]  B. Simon,et al.  Infrared bounds, phase transitions and continuous symmetry breaking , 1976 .

[20]  E. Lieb.  The classical limit of quantum spin systems , 1973 .

[21]  N. Mermin,et al.  Absence of Ferromagnetism or Antiferromagnetism in One- or Two-Dimensional Isotropic Heisenberg Models , 1966 .

[22]  Philip W. Anderson,et al.  New Approach to the Theory of Superexchange Interactions , 1959 .

[23]  Freeman J. Dyson,et al.  General Theory of Spin-Wave Interactions , 1956 .

[24]  F. Dyson.  Thermodynamic Behavior of an Ideal Ferromagnet , 1956 .

[25]  W. Pauli,et al.  Über Gasentartung und Paramagnetismus , 1927 .