Session I26 - Magnetic Nanostructures and Heterostructures VI: Magnetic Microstructure.
MIXED session, Tuesday afternoon, March 21
211A, MCC
It has been shown that, when a strong static magnetic field B is applied in the plane perpendicular to the columnar axis of a thin-film composite medium with a periodic two-dimensional or columnar microstructure, surprising anisotropies may appear in the microstructure-induced magnetoresistance [1]. More recently, it was found that, in a two-constituent normal conductor/perfect conductor random columnar mixture the induced in-plane magnetoresistance saturates if B is very strong. By contrast, in a normal conductor/perfect insulator mixture this magnetoresistance keeps increasing as B^2 without ever saturating [2]. I now report that in a three-constituent random columnar mixture of normal conductor, perfect conductor, and perfect insulator the induced magnetoresistance switches from saturating to nonsaturating B^2 behavior when the volume fractions of the perfect conductor and perfect insulator are equal. This is a second-order-phase-transition-like singularity, with critical exponents and scaling behavior as expected for such a critical point.
[1] M. Tornow, D. Weiss, K. v. Klitzing, K. Eberl, D. J. Bergman, and Y. M. Strelniker, Phys. Rev. Lett. 77, 147 (1996).
[2] D. J. Bergman and Y. M. Strelniker, Phys. Rev. B 60, 13016 (1999).