Measurement of Magnetic Hysteresis Loops of the Ni-5at.%W Alloy Substrate as a Function of Temperature in a Stack of 2G HTS-Coated Conductor Annuli

Abstract

The development of coated conductors with a ferromagnetic substrate and their use in various applications require an accurate knowledge of the magnetic properties of the substrate. In this work, we report measurements in AC regime (30 Hz) of the magnetic hysteresis loops of the Ni-5at.%W alloy ferromagnetic substrate in a stack of 2G YBCO tapes cut in the shape of annuli from 46 mm wide coated conductors. The stacked annuli form a closed magnetic circuit which is the ideal configuration due to the absence of demagnetizing effect. The measurements are carried out at four temperatures between 77 K and 293 K. The peak intensity of the relative permeability is not significantly affected in the range of temperature considered. The coercive field dependence with temperature is also investigated. The hysteresis losses Q as a function of the amplitude of the flux density Bm exhibit a power law behavior (Q ∼ B n m ) at the four temperatures. This power law behavior is also studied at low fields under the presence of a DC bias field. Finally, the hysteresis loops can be reproduced with the Jiles-Atherton model, which is used to estimate the hysteresis parameters and to discuss their temperature dependence.

Magnetic shielding up to 0.67 T at 77 K using a stack of high temperature superconducting tape annuli of 26 mm bore

“…When B app > 15 mT the flux density in the material globally exceeds 100 mT. As a result, when the applied field is in the range 15 mT < B app < 60 mT, most of the material is located on the descending part of the µ r (B) dependence reported in [69]. This justifies the decreasing SF shown is figure 12(a).…”

“…When a field-dependent permeability µ r (B) is considered, the SF is found to decrease with the applied field monotonically up to 60 mT. This result may look paradoxical since µ r (B) at 77 K increases in this field range [69], corresponding also to the increasing part of the permeability vs. magnetic field in the ferromagnetic substrates µ r (H) curve shown in Figure 3. The explanation comes from the fact that the (non-uniform) magnetic flux density inside the FM when the stack is used to shield an applied transverse field H app might be higher than the uniform flux density B app = µ 0 H app .…”

“…The (x, y, z)-coordinates system is shown in Figure 1. The field dependence of the relative permeability µ r (H) of the ferromagnetic substrate was measured in a previous work on the same sample [69] at both room temperature and 77 K. For the modelling, we use an interpolation of the experimental relative permeability at each temperature: the corresponding data are plotted in Figure 3.…”

Measurement and Analysis of Magnetic Properties of Permalloy for Magnetic Shielding Devices under Different Temperature Environments

“…According to the results, these properties have been shown to be negatively correlated with temperature. Brialmont et al [24] proved that by measuring Ni-5at.%. The relative permeability and peak strength of the relative permeability of the W alloy are almost unaffected within the test temperatures of 77 K, 195 K, 238 K, and 297 K, respectively.…”

Measurement and analysis of an optimized Jiles–Atherton model considering the influence of temperature applied in magnetic shielding devices

“…Panakhov et al [18] proved that the temperature dependence of the differential thermoelectric potential of permalloy can be used to make thermocouples. Brialmont et al [19] tested the relative permeability of Ni-5at.%W alloy at four temperatures between 77 K and 293 K and proved that the peak strength has no significant effect in the considered temperature range. Xiao et al [20] measured the magnetic properties of silicon steel under the temperature and pressure coupling environment, indicating that the relative permeability increases with the increase in temperature, while the influence of pressure on the magnetic properties decreases with the increase in temperature.…”