these measurements the following conclusions can be drawn:1. The value of the surface anisotropy obtained from our measurements is in good agreement with the theoretically computed value 10) and with the exchange surface anisotropy 11) and has the order of K s observed experimentally by means of thin films spin-wave resonance 12).2. The irregularities of the surface play a minor role in line broadening as shown by the small difference between whiskers and electrolytically polished crystals having largely differing surface state s.3. The line broadening due to an increase of the measured area indicates that here the inhomogeneity of the demagnetising field begins to assert itself.4. The agreement between the theory referred to above and the experimental results on bulk silicon iron single crystals is good. It is proof that, at least in some metallic ferromagnets having few imperfections, the intrinsic resonance linewidth (without skin effect and surface anisotropy broadening) is under 10 Oe.

The problem of determining the eigenstates of the pairing-force Hamiltonian is reformulated in terms of the eigenstates of a many-boson system with an N-body interaction. The N-body interaction includes the effects of the Pauli principle on the eigenstates of the pairing-force Hamiltonian. Explicit expressions for four types of eigenstates are derived. These four types are the eigenstates of N pairs in one or two multiply degenerate single-particle levels, the one-pair eigenstates and a new restricted class of N-pair eigenstates.

No abstract

Expressions for the ground and excited state energies of a system of nucleons interacting through pairing forces are given as a power series in inverse powers of the number of particles. The expressions are valid for systems with superfluid ground states and either J=0 or L=0 pairing. The first three terms in the expansion are given explicitly, and they exhibit excitations with both vibrational and rotational (in isospin space) character. Analytical and numerical results are given for a model system with a two-level single-particle spectrum.