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

Magnetic nanowires (NWs) are critical components in fields such as data storage and spintronics, where precise control of their magnetic properties is essential for device optimization. The behavior of isolated NWs 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 NWs and single ones is often poorly characterized, as measuring individual NWs 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 a few individual Ni NWs with $(72\ifmmode\pm\else\textpm\fi{}5)$ 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 NWs and the array, we show that coercivity values of individual NWs are at least twice as large as for the array in the range 5--200 K. Also, we characterize the differences in the hysteresis loops, which are more squared for isolated NWs, with a high magnetic remanence $\ensuremath{\sim}80%$ of the saturation value. Our results highlight the crucial role of dipolar and mechanical interactions in modifying the magnetic behavior of NW arrays, providing valuable insights for the design and application of NW-based magnetic devices.