Search

The temperature dependences of the d.c. magnetic susceptibility and Verdet constant in two zirconium based fluoride glasses have been studied. One sample has as a minor constituent dysprosium which has a large magnetic moment that dominates the material's magnetic character. The second sample, containing a small amount of europium, shows both Van Vleck paramagnetism and a Curie-Weiss behaviour. The Curie-Weiss character is believed to come from small amounts of and/or produced during the sample's manufacturing process. An upper limit is placed on the amount of magnetic zirconium in the material.

It is shown that a relatively small non-linear behavior of the velocity drive system used in Mossbauer effect studies yields pseudo-discontinuities in the isomer shift near the critical temperatureT c of a magnetic-paramagnetic transition. The anomaly of the57Fe isomer shift in iron is attributed to this effect.

A furnace system is presented for Mossbauer‐effect spectroscopy at temperatures up to 1200 K with a temperature stability better than 0.03 K. This system allows the study of samples at high temperatures in an external magnetic field of a few kG with a homogeneity of better than 1%. Our measurements show that a few degrees above the Curie temperature TC, such an external field induces a considerable hyperfine field at 57Fe nuclei in iron. In addition, the magnetic hyperfine field and the isomer shift of 57Fe in metallic iron are measured over a temperature range of 300 to 1100 K. It is shown that a relatively small nonlinear behavior of the Mossbauer velocity drive system may result in a pseudodiscontinuity in the isomer shift δ near the Curie temperature, explaining the anomalous behavior observed for δ of iron and of some iron alloys in this region.

The recoilless fractionf of57Fe in iron is determined as a function of temperatureT in the vicinity of the Curie temperatureTc using a source of57Co diffused in a foil of 100% enriched56Fe. Our results show thatf does not undergo an abrupt change atTc, but that in the ferromagnetic phase |df/dT| is larger than in the non-ferromagnetic phase. This indicates that the ferromagnetic interaction increases the bond between the iron atoms, and thus contributes to the stability of the iron lattice belowTc.

Theoretical as well as experimental investigations were carried out for the propagation of leaky waves along an important class of optical thin‐film waveguides. For this type of guiding structure which may consist of heteroepitaxial deposition of ZnS or ZnSe on GaAs, the dielectric constant of the thin film is less than that of the substrate. Consequently, only the leaky type of guided waves may exist. Theoretical results show that the attenuation constants of leaky modes, which may be TE or TM, are inversely proportional to (thickness of layer)3 and directly proportional to (wavelength)2, and that TM modes are more lossy than TE modes. The existence of these leaky modes has also been demonstrated for three different thicknesses.