Resistivity Minimum in Granular Composites and Thin Metallic Films

TL;DR

This paper investigates how the electrical resistivity in granular ferromagnetic materials and thin metallic films exhibits a minimum at certain temperatures, linked to their granular structure and tunneling effects.

Contribution

It provides a detailed analysis connecting resistivity minima to the granular structure and tunneling mechanisms in ferromagnetic compounds and thin films.

Findings

Resistivity minimum arises from a transition between intra-granular metallic conductance and inter-granular tunneling.

Logarithmic variation of conductivity observed at low temperatures.

Resistivity behavior explained by granular structure and tunneling effects.

Abstract

We analyze the temperature dependence of conductivity in thick granular ferromagnetic compounds NiSiO2 and in thin weakly coupled films of Fe, Ni and Py in vicinity of metal-insulator transition. Development of resistivity minimum followed by a logarithmic variation of conductivity at lower temperatures is attributed to granular structure of compounds and thin films fabricated by conventional deposition techniques. Resistivity minimum is identified as a transition between temperature dependent intra-granular metallic conductance and thermally activated inter-granular tunneling.