Analysis of the alternating current conductivity and magnetic behaviors for the polycrystalline Y-type Ba0.5Sr1.5Co2(Fe1-xAlx)12O22 hexaferrites

Abstract

Co2Y hexaferrites have attracted intensive interests due to its potential high temperature magnetoelectricity as the single phase multiferroics. Numerous efforts have been paid to enhance their magnetoelectric properties at high temperatures through increasing the magnetic transition temperature and decreasing the conductivity. In this work, we investigated the conductivity and magnetic properties of the polycrystalline Ba0.5Sr1.5Co2(Fe1−xAlx)12O22 (0 ≤ x ≤ 0.12) hexaferrites and found that Al-doping has important effects on both the conductivity and magnetic properties. The underlying physical mechanisms were also systematically analyzed. Most importantly, a very much enhanced resistivity (over 10 MΩ cm), and a high magnetic transition temperature (∼346 K) have been obtained at a doping amount of x = 0.04. These improvements are very promising for achieving significant magnetoelectric effect at room temperature. The current research can provide the basic understanding of the Y-type ferrites for future applications in magnetoelectric and other fields.

Field‐Dependent Magnetoelectric Effects in Polycrystalline Co2Y‐Type Ba0.5Sr1.5Co2(Fe1−xAlx)12O22 Hexaferrites

“…However, with large amount of doping ( x > 0.08), a small amount secondary phase Fe 3 O 4 is detected. Compared with our previous work, the impurity phase BaFe 2 O 4 was disappeared, which is due to the high‐purity raw material of Fe 2 O 3 .…”

“…Polycrystalline Y‐type Ba 0.5 Sr 1.5 Co 2 (Fe 1− x Al x ) 12 O 22 ( x = 0, 0.04, 0.08, 0.12) hexaferrites were prepared by the conventional solid‐state reaction method. The experimental procedure is similar as our previous work . Analytic reagent‐grade raw materials of SrCO 3 (99%), BaCO 3 (99%), Al 2 O 3 (99%), Co 3 O 4 (99%), and high‐purity (4N) Fe 2 O 3 were weighed and thoroughly mixed through ball milling with agate media in ethanol for 4 h. The mixtures were dried and presintered at 1000°C for 10 h. They were then milled again and dry pressed into cylindrical pellets with approximately 11.5 mm in diameter and 2‐3 mm in thickness.…”

Electric and magnetic properties of Y-type Ba2Mg2Fe12O22 hexaferrites with various Co doping

“…(Refs. [12,20,22]). In region II, the values of E rel are 0.53-0.62 eV for all samples, which are comparable to those obtained in other works [30,31], indicating that the relaxation carries are the oxygen vacancies [31][32][33][34].…”

“…Fe 2? become more active [12]. Therefore, the dielectric constant increases with increasing cobalt content.…”

“…The dielectric constants for Y-type hexaferrites can be as high as 10 4 -10 6 and show dispersion at low frequencies [12][13][14]. These phenomena were discussed based on the Maxwell-Wagner model [15,16] and Koop's phenomenological theory [17] in connection with the inhomogeneous structure of sample.…”