Bi-magnetic microwires: a novel family of materials with controlled magnetic behavior

A novel technique involving combined sputtering and electroplating procedures has been recently developed to deposit metallic (magnetic or not) nano and microlayer tubes onto glass-coated amorphous magnetic microwires to enable the tailoring of their magnetic behavior. Here, after introducing the general aspects of that technique, we present the latest results on a new family of two-phase magnetic samples: bi-magnetic multilayer microwires. They consist of a magnetically soft nucleus (typically a Fe or Co base amorphous microwire, coated by Pyrex layer) onto which a 30 nm thick Au layer is first sputtered followed by the electroplating of a harder microlayer, namely Co x Ni(1-x) layer, with x controlled by the current density during electrodeposition whose micrometric thickness is also controlled by plating time. The hysteresis loops present a two-step reversal process typical of two-phase magnetic material. The magnetization reversal of the soft nucleus and the harder layer takes place at around 1 Oe and up to about 200 Oe, respectively. The presence of sputtered and electroplated layers induces significant stresses in the soft magnetic nucleus that modify its magnetization easy axis. This technique allowing us the tailoring of the magnetic behavior of multilayer magnetic microwires opens new possibilities for applying these novel materials as sensing elements in various devices