M - H loop tracer based on digital signal processing for low frequency characterization of extremely thin magnetic wires

Abstract

A high-sensitivity ac hysteresis loop tracer has been developed to measure the low frequency hysteresis loop of soft magnetic materials. It has been applied successfully to characterize straight pieces of amorphous glass-covered microwires with metallic nucleus down to 1.5 microm thick. Based on the electromagnetic induction law, the proposed design is extremely simple and exploits the capabilities of commercially available data acquisition cards together with digital signal processing in order to achieve high-sensitivity without the need of expensive analog equipment.

Ultrathin Nanocrystalline Magnetic Wires

“…The length of the samples measured with this system is about 4 cm, whilst the diameter can take any value between 90 and 1000 nm. The technique, which employs the so-called window method [34], works for any magnetically bistable ultra-thin wire, and the resulting hysteresis loop is a noise-free one, as illustrated in the following section. suitable for magnetically bistable samples, which always exhibit rectangular hysteresis loops, and is based on a digital integration technique.…”

“…The length of the samples measured with this system is about 4 cm, whilst the diameter can take any value between 90 and 1000 nm. The technique, which employs the so-called window method [34], works for any magnetically bistable ultra-thin wire, and the resulting hysteresis loop is a noise-free one, as illustrated in the following section. The domain wall velocity has been measured using an improved Sixtus-Tonks technique, with four pick-up coils, to allow the detection of walls with any additionally nucleated domains that could alter the precision of the measurements.…”

Rapidly Solidified Magnetic Nanowires and Submicron Wires

“…Given the ultra-small diameters of rapidly solidified submicron wires and nanowires (metallic nucleus diameters between several tens of nanometers and hundreds of nanometers), the use of the classical characterization techniques employed for typical microwires with diameters between 1 and 50 m (Butta et al, 2009;Kulik et al, 1993) in order to measure their basic magnetic properties, e.g. to determine their magnetic hysteresis loops, is not viable due to the low sensitivity and signal-to-noise ratio (SNR).…”

“…The SNR is still too small to obtain a good integration. Therefore, a window method has been employed (Butta et al, 2009). Considering that everything outside the peak area of the signal must be zero, two windows were used to select the peak area from the sample signal while the rest of the noisy signal was numerically forced to become null.…”

Low-field magnetization process and complex permeability of FeCoBSiTa wires coated with hard magnetic CoNi layer

“…The magnetic properties (i.e. M-H hysteresis loops and their parameters) were measured by inductive methods at 50 Hz using M-H loop tracer based on digital signal processing for low frequency, which reaches a maximum magnetic field of 2·1 kA/m (Butta et al 2009). Complex permeability, μ * = μ re + jμ im , was determined from complex impedance, Z * = Z re + j Z im , measured according to the relation (Valenzuela 2004(Valenzuela , 2007:…”