Coercivity and Interactions in Sr–M Thin Films with Nonperpendicular Orientation

Abstract

Magnetic viscosity and interactions have been studied recently in bulk M‐type hexaferrites. Herein, this kind of study is extended to Sr–M (SrFe12O19) thin films deposited on SiO2/Si substrates using the pulsed laser ablation technique at relatively low substrate temperatures at 2.7 mbar oxygen atmosphere. Samples are characterized by X‐ray diffraction, scanning electron microscopy, and vibrating‐sample magnetometry. The high values of the coercive field (4.8 kOe) obtained for the films are in correspondence with large values reported in thin films, powders, and sintered samples for the Sr–M compound. Demagnetization‐like interactions are found and magnetic viscosity results point to the coercivity mechanism different from coherent rotation despite the small particle size.

Coercivity, Activation Volumes, and Interactions in BaFe12O19

“…In this expression, H a‐eff corresponds to the effective anisotropy field and χ o corresponds precisely to the initial susceptibility. With the values obtained for the saturation magnetization and fitting that initial part of the magnetization curve, a value of H a‐eff = 13 300 Oe was obtained and from this a value H c‐fit = 0.48 H a‐eff = 6400 Oe was calculated, for Bacop at 300 K. Note that it can also be expressed that H a‐eff = H a − N eff M s , and from here an effective N , ( N eff ), can be calculated using the value of the anisotropy field H a reported for BaM [ 16 ] and the experimental value obtained for saturation magnetization. Thus, a value of N eff = 10 was obtained.…”

“…[8][9][10][11][12][13] Despite these novel properties, in M hexaferrites there are open issues associated to mechanisms of magnetization reversal and magnetic relaxation. [14][15][16] As the grain size is reduced and multidomain state becomes unfavorable, magnetization reversal must occur by coherent or incoherent processes and therefore aspects such as interparticle interactions come to be more important. In relation to that, a study on SrFe 12 O 19 (Sr-M) samples prepared using different methods was previously reported.…”