Magnetic and structural characteristics of self-assembly Co-Ni-Zn ternary nanocrystals

Abstract

With respect to the rapid growth of high-performance applications for magneto-electric alloys, extensive attempts have been made to develop the electroplating of nanocrystalline magnets coatings within high coercivity and excellent corrosion resistance. Herein we proposed a low-cost and practical electroplating of the substitution of Zn2 + ions in Ni-Co bath for the ternary Ni-Co-Zn soft-magnetic alloys. Anomalous co-deposition of Ni0.12Co0.88-xZnx (x = 0–0.36) alloys were aligned from sulfamate electrolytes within L-ascorbic acid (H2Asc) as complexant, in which the ratio (x) of atomic molar was regulated by dropping ZnCl2 concentrated solution based on Nernst theory and Cyclic-Voltammetry (CV) tests. Results validated that it yielded crystal growth within a narrow size of 150–250 nm, allowing the structural recombination of the spider-web-like ZnO tangled with Ni-Co nanocrystals. In addition to the enhanced corrosion behavior of the ternary Ni-Co-Zn alloys compared to binary Ni-Co, it was attributed to the coexistence of γ-Ni5Zn21 phase and [Zn(OH)4]2- colloidal-like corrosion products. More impressively, it depicted high coercivity (Hc) of ∼15.3 Oe and superior saturation magnetization (Ms) of ∼153.2 emu/g from VSM tests for Ni0.12Co0.64Zn0.24 (x = 0.24), which was due to the self-assembly of ZnO-rich dispersoids twined around GB regions to be magnetic isolation and restrict the movement of domain walls for higher coercivity. Especially for the sample (x = 0.24) after aged at 450 °C for 2 h, it achieved a superior Hc value of 45.8 Oe that was 3 times higher than those without ageing, which was correlated well with large internal stresses by the disordered stacking among hetero-atoms. So the integrated Ni-Co-Zn ternary soft magnets offered a promising approach to achieving high coercivity with excellent anti-corrosive properties, satisfying the stringent requirements of potential applications used in magnetic memory devices, etc.