Visualization of Magnetic Flux in Magnetic Materials and High Temperature Superconductors Using the Faraday Effect in Ferrimagnetic Garnet Films

Abstract

Perhaps one of the greatest discoveries of this century was the phenomenon of superconductivity. A Dutch physicist, Haike Kamerlingh Onnes at the University of Leiden first made this discovery in 1911 [1] when examining the current carrying properties of metallic mercury at low temperatures, with the aid of his newly acquired ability to liquify helium. Seventy five years later in 1986, two physicists J. George Bednorz and K. Alex Muller at the IBM research laboratory in Zurich, Switzerland discovered the first of a new class of High Temperature Superconductors (HTS) [2]. They reported the observation of superconductivity in the lanthanum copper oxides with transition temperatures up to 38K. The real excitement began less than one year later with the discovery of YBa2Cu3O7) a superconducting material with a transition temperature of 92K [3], well above the temperature of liquid nitrogen. This indicates the beginning of the era of high-temperature superconductivity. As a snowy ball rolls from the top of a hill, this achievement generated an enormous new interest in superconductivity, and as a result many new compounds have been synthesized since 1988. These include bismuth lead strontium calcium copper oxides with Tc ~ 105K [4], thallium barium calcium copper oxide with Tc=125K [5] and the mercury compounds [6] with an upper Tc=133K.