Double Percolation Transition in Superconductor/Ferromagnet Nanocomposites

TL;DR

This study reveals a double percolation transition in superconductor/ferromagnet nanocomposites, showing high resistance states between two thresholds due to interface effects, with distinct critical behaviors.

Contribution

It uncovers the phenomenon of double percolation transitions in binary nanoparticle networks and analyzes their critical scaling behavior at low temperatures.

Findings

High-resistance state observed between two percolation thresholds

Distinct critical exponents identified for each transition

Double percolation effect controlled by composite volume fraction

Abstract

A double percolation transition is identified in a binary network composed of nanoparticles of magnesium diborade superconductor and chromium oxide half-metallic ferromagnet. Anomalously high-resistance or insulating state, as compared to the conducting or superconducting states in single-component systems of either constituent, is observed between two distinct percolation thresholds. This double percolation effect, which is especially pronounced at liquid helium temperatures, is controlled by composite volume fraction and originates from the suppressed interface conduction and tunneling between nanoparticles of different species. We investigate the scaling behavior near both percolation thresholds, and determine the distinct critical exponents associated with two different types of transitions.