Magnetic volcanos in gadolinium Langmuir-Blodgett films

Magnetic, structural and electronic properties of Langmuir-Blodgett films w ith incorporated Gd3+ ions has been detected using a scanning DC SQUID micr oscope, scanning electron microscope and X-ray diffraction. The magnetic im ages of 28 and 50 layer thick films at 77 K have been obtained after in-pla ne and out-of-plane pre-magnetization in a field of 1.4T at 300K. Randomly placed "magnetic volcanos" with a remanent magnetic moment of the order of 10(-13) A m(2) was observed. A decay of the remanent magnetization with a c haracteristic time of about 120 h was observed. It is suggested that the ma gnetic order is relatively long ranged, and that topological defects (vorti ces) lead to the observed out-of-plane field lines, and are responsible for the magnetic volcanos. Finally, it is hypothesized that a similar topology of field lines is responsible for superconductivity as observed in ceramic high-T-C superconductors. (C) 2001 Elsevier Science B.V. All rights reserv ed.