High magnetization Co-GdOx superparamagnetic granular films as magnetic coating materials for high-sensitivity alternating magnetic force microscopy tip

JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS

卷:462

Article

Cao, Yongze¹  Kumar, Pawan²  Zhao, Yue¹  Suzuki, Yudai²  Yoshimura, Satoru²  Saito, Hitoshi² 

[1] Akita Univ, Reg Innovat Ctr, Tegata Gakuen Machi 1-1, Akita 0108502, Japan

[2] Akita Univ, Grad Sch Engn Sci, Tegata Gakuen Machi 1-1, Akita 0108502, Japan

关键词: Superparamagnetic;    Co-GdOx;    Magnetic field sensor;    Granular film;    Initial susceptibility;   

DOI  :  10.1016/j.jmmm.2018.04.065

来源: Elsevier

【 摘 要 】

The Co-y(GdOx)(1 y), CoyAg1 y, (Fe70Co30)(y)(AlOx)(1 y) superparamagnetic (SP) granular films were fabricated by magnetron co-sputtering technique and compared for their magnetic properties. The effect of the different matrix (GdOx, Ag, AlOx) is investigated for refining and separating magnetic particles in nonmagnetic matrix by calculating the magnetic volume fraction (y), and the results indicate that the GdOx matrix can more effectively refine and separate magnetic particles. The Co-0.44(GdOx)(0.56) SP film with the maximum Co volume fraction (y = 0.44) approaches the highest magnetization of 608 emu/cm(3) at 20 kOe, and initial susceptibility (1.74 x 10 (5) H/m) as compared with Co-Ag, Fe70Co30-AlOx films and some systems of other researchers at room temperature (RT). The magnetic particle size and size distribution in these SP films is calculated by fitting with Langevin function and the results of calculation are consistent with the high-resolution transmission electron microscopy (HRTEM) results. To further confirm the SP behavior, the blocking temperature of the Co-0.44(GdOx)(0.56) film with the maximum Co volume fraction is measured as similar to 145 K, which is below RT. Finally, the Co-0.33(GdOx)(0.67) thin film having a linear magnetization curve is used for the fabrication of the SP tip and further used for the A-MFM measurement on the bulk Sr-Ferrite (SrF) magnet. The fabricated Co-0.33(GdOx)(0.67) SP tip along with A-MFM shows an excellent result as compared to the state of art FePt hard magnetic tip using conventional MFM, and it can directly detect the intensity and identify the polarity of the stray field originating from a bulk Sr-Ferrite (SrF) permanent magnet without topography crosstalk in ambient atmosphere. (C) 2018 Elsevier B.V. All rights reserved.

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