Nonmagnetic Ones Research Articles

Application of ferromagnetic resonance probes to the characterization of flaws in metals

This article presents some results obtained in the characterization of surface flaws by means of probes using ferromagnetic resonance of yttrium iron garnets (FMR probes). These experiments on artificial flaws show that FMR probes operate like eddy current probes for nonmagnetic materials and like magnetic field sensors for magnetic ones. Consequently, the working distance is larger for magnetic materials (1000–1500 µm) than for nonmagnetic ones (100–300 µm). FMR probes have good sensitivity to narrow flaws, good spatial discrimination, and are sensitive to flaw width and depth. Vector analysis allows the separation of distance and flaw effect by phase analysis on nonmagnetic materials. On magnetic materials this phase separation does not exist and another procedure is suggested. These results, and in particular those obtained on ferromagnetic materials, point to the possibility of replacing some eddy current or magnetic particle inspections by tests with ferromagnetic resonance probes.

Magnetic properties of multilayered Fe-Si films

The coercivity and permeability of Fe-Si films can be improved by laminating several layers with either nonmagnetic (SiO2, Al2O3, Al or Mo) or ferromagnetic (Ni, Fe, Co or 20-wt. % Fe–Ni) spacers. It is also found that films made with soft magnetic laminations have an advantage over nonmagnetic or hard magnetic ones. Such behavior is concluded to be attributed to the smaller grain size, and pinhole or exchange coupling of multilayered Fe-Si films by observing domain and grain structures.

One-dimensional random magnetic lattice gas

We consider a lattice gas, in which particles possess magnetic moments of random values. There are two kinds of interactions — magnetic and nonmagnetic ones. Equations of state are derived in one dimension and the resulting phase diagrams are constructed and the influence of the distribution width and coupling constants strength is discussed.

Specific heat discontinuity of a proximity-effect sandwich system containing Kondo impurities

The theoretical work of Matsuura, Ichinose, and Nagaoka on the Kondo effect in superconductors and McMillan's tunneling model are applied to a proximity-effect sandwich system containing Kondo impurities. Analytic expressions for the renormalized Green's functions of superconducting and normal-metal electrons are given as functions of the system composition. It is found that as the thicknesses become large, the specific heat discontinuity changes continuously from the Muller-Hartmann-Zittartz value for the magnetic cases to the Ichinose value for the nonmagnetic ones. For small values of the layer thickness, and with the films in proximity, our results can be used to calculate the specific heat jump at the transition temperature numerically.

Parametersκ1,κ2, andκ3in magnetic superconductors

The parametrization to describe the magnetic properties of superconductors, ${\ensuremath{\kappa}}_{1}(t){\ensuremath{\kappa}}_{2}(t)$, and ${\ensuremath{\kappa}}_{3}(t)$, is extended to the case of magnetic superconductors in such a way that the effects of average polarization are subtracted. In this extension, ${\ensuremath{\kappa}}_{1}(t)$, ${\ensuremath{\kappa}}_{2}(t)$ approach the same value $\ensuremath{\kappa}$ in the limit $t\ensuremath{\rightarrow}1$. It was shown that when the electromagnetic interplay is the main mechanism in the magnetic superconductors, ${\ensuremath{\kappa}}_{1}(t)$, ${\ensuremath{\kappa}}_{2}(t)$ [and ${\ensuremath{\kappa}}_{3}(t)$] are related to the nonmagnetic ${\ensuremath{\kappa}}_{1}(t)$ 's by the simple scaling rule near the critical temperature. In this case, it is also shown that the magnetization curve can be obtained by a suitable scaling of fields and $\ensuremath{\kappa}$ from the nonmagnetic ones. Especially, types of the magnetization curve are classified not in terms of $\ensuremath{\kappa}$ but in terms of the the scaled ${\ensuremath{\kappa}}^{\ensuremath{'}}$ {$\ensuremath{\equiv}\frac{\ensuremath{\kappa}}{{[1+4\ensuremath{\pi}\ensuremath{\chi}(t)]}^{\frac{1}{2}}}$, where $\ensuremath{\chi}(t)$ is the static spin susceptibility} near the critical-temperature region. Several relations related to the magnetic properties are also presented. The practical usefulness of our formulation lies in the fact that it presents a simple way of obtaining the magnetization curves of magnetic superconductors from those of nonmagnetic ones.

Direct Conductance Method of Measuring Casing Lengths

AbstractThe standard water‐level indicator can be easily and inexpensively modified so that it also measures casing lengths. The simple modification permits electrical current from one wire of the two‐wire probe to be routed through the metal casing. The semiquantitative method works well with most metal casings, including nonmagnetic ones, and can be used to detect most casing reductions. The method is limited in that it works only below the water level in the well, and in that it cannot easily detect casing reductions when the conductance between the upper and lower casings is low.

APPLICATION OF THE BETHE-WEISS METHOD TO THE STATISTICAL THEORY OF FERROMAGNETISM OF SUBSTITUTIONAL SOLID SOLUTIONS

The Bethe-Weiss method in the statistical theory of Heisenberg ferromagnetism is generalized and applied to the case of subtitutional solid solutions of random distribution. Calculations are carried out for binary solutions containing magnetic atoms of spin 1/2 and nonmagnetic ones. The Curie temperature v.s. composition and the paramagnetic susceptibility v.s. temperature curves are obtained for simple and body-centered cubic lattices. The degree of magnetic short-range order at the Curie point becomes higher as the concentration of non-magnetic atoms increases. The results are qualitatively applicable to solutions of two different kinds of magnetic atoms. It is also concluded that the method gives an useful approximation only for higher concentrations of magnetic atoms.