Temperature dependence of coercivity for isolated Ni nanowires unraveled by high-sensitivity micromagnetometry

TL;DR

This study investigates how temperature affects the coercivity of isolated Ni nanowires using high-sensitivity micromagnetometry, revealing significant differences from nanowire arrays due to dipolar and magnetoelastic interactions.

Contribution

It demonstrates the use of a highly-sensitive micromechanical torsional oscillator to measure individual nanowires, providing new insights into their magnetic behavior compared to arrays.

Findings

Individual nanowires have at least twice the coercivity of arrays between 5 K and 200 K.

Isolated nanowires exhibit more squared hysteresis loops with high remanence (~80%).

Dipolar and mechanical interactions significantly influence nanowire magnetic properties.

Abstract

Magnetic nanowires are critical components in fields such as data storage and spintronics, where precise control of their magnetic properties is essential for device optimization. In particular, the behavior of isolated nanowires is often different from that of an ensemble, offering an opportunity to explore the role that dipolar and magnetoelastic interactions play in the latter system. Unfortunately, the comparison between a collection of nanowires and single ones is often poorly characterized, as measuring individual nanowires with weak magnetic signals is a challenging task. In this work, we employ a highly-sensitive micromechanical torsional oscillator to measure the magnetic response of few individual Ni nanowires with 72 +/- 5 nm average diameter, fabricated by electrodeposition in anodic aluminum oxide templates as an array and subsequently released from this membrane. When comparing the magnetic properties as a function of temperature between single nanowires and the array, we show that coercivity values of individual nanowires are at least twice as large as for the array in the range 5 K - 200 K. Also, we characterize the differences in the hysteresis loops, which are more squared for isolated nanowires, with a high magnetic remanence close to 80 % of the saturation value. Our results highlight the crucial role of dipolar and mechanical interactions in modifying the magnetic behavior of nanowires arrays, providing valuable insights for the design and application of nanowires-based magnetic devices.