Structural, Morphological, Electrical Resistivity, and Temperature-dependent Magnetic Property of Single-layered Amorphous Fe70Co15Zr7B5Cu3 HITPERM Films: The Effect of Thickness

Abstract

Soft magnetic films play a crucial role in numerous technological applications, such as magnetoelectronics, telecommunications, and magnetic recording, and the tuning of properties to obtain high-efficiency demands searching new materials and controlling thickness and compositions. In this regard, we report a systematic investigation of structural, morphological, electrical resistivity, and temperature-dependent magnetic properties of single-layer amorphous Fe₇₀Co₁₅Zr₇B₅Cu₃ HITPERM (t = 5–100 nm) films deposited on a low-cost thermally oxidized Si substrate. Structural studies (XRD and TEM) reveal an amorphous nature in all as-deposited films. Surface morphology shows that the average roughness increases with increasing t up to 50 nm and then decreases at higher thicknesses. The electrical resistivity decreases rapidly as t increases from 5 to 10 nm and then is invariant for films with t ≥ 30 nm. Interestingly, the variation of resistivity follows the Boltzmann fitting. These films exhibit tunable magnetic properties between soft (t < 20 nm) and semi-hard (20 nm < t < 70 nm) properties with rectangular-type magnetic hysteresis loops having ~ 100% remanence ratios (M_r/M_s), low coercivity (H_c < 2.5 kA/m), and low saturation magnetic field (H_s < 3 kA/m) for t ≤ 70 nm. Transcritical hysteresis loop with a large H_c > 6.7 kA/m, high H_s > 26.5 kA/m, and reduced M_r/M_s ~ 55% is observed for t = 100 nm film. High-temperature thermomagnetization curves display two magnetic phase transitions (T_C) corresponding ferromagnetic state to a paramagnetic state of the amorphous phase (at 820 K during warming) and nanocrystalline phase (at 1003 K during cooling). The observed results of HITPERM films with large T_C naturally make it a potential choice for applications not only in magnetoelectronics at room temperature but also for aircraft power devices at higher temperatures.