Heat‐treatment influence on the microstructure and magnetic properties of rare‐earth substituted SrFe12O19
Heat‐treatment influence on the microstructure and magnetic properties of rare‐earth substituted SrFe12O19
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热处理对稀土取代SrFe12O19显微组织和磁性能的影响
DOI：
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发表时间：
2006
期刊：
影响因子：
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通讯作者：
N. Rezlescu
中科院分区：
文献类型：
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作者：
C. Doroftei;E. Rezlescu;P. Popa;N. Rezlescu
采用溶胶-凝胶-自燃烧法制备了稀土取代的锶铁氧体纳米粉体SrFe 12-xRxO 19（R = La，Gd和Er; x = 0.2，0.5和1）。采用X射线衍射仪、振动样品磁强计和扫描电子显微镜对在800、900和10000 ℃下热处理不同时间的SrFe 12-xRxO 19粉末的结构和磁性进行了表征。X射线衍射测量的结果表明通过热处理形成了M型六方结构。热处理条件（温度和时间）决定了合金的磁性能，如比饱和磁化强度σs、比剩磁σr和矫顽力Hc，以及合金的微观结构。在临界热处理时间后，合金的矫顽力Hc有很大的增加。当热处理时间增加时，在较短的热处理时间之后获得Hc的增加。Hc的这种跳跃是由单畴纳米颗粒从超顺磁态到正常态的转变来解释的。磁相互作用的超细微晶组成的团聚结构的发生也有助于增加Hc。热处理决定了减少晶粒生长由于由R离子产生的内应力。随着R含量的增加，由于R离子溶解到六角铁氧体晶格中，σs和σr减小。我们认为，通过选择热处理的时间和温度，可以获得适合磁记录介质应用的显微组织和磁性能。（© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA，魏因海姆）
Rare‐earth substituted strontium ferrite nanopowders SrFe12‐xRxO19 (R = La, Gd and Er; x = 0.2, 0.5 and 1) were prepared by sol‐gel‐autocombustion method and subsequent heat treatments. Structural and magnetic properties of SrFe12‐xRxO19 powders heat treated at 800, 900 and 10000C, for various times, were characterized with an X‐ray diffractometer, a vibrating sample magnetometer and a scanning electron microscope. The results of X‐ray diffraction measurements showed the M‐type hexagonal structure formation by heat treatments. Magnetic properties, such as specific saturation magnetization σs, specific remanent magnetization σr and coercivity Hc, as well as microstructure depend on the heat treatment conditions (temperature and time). The coercivity Hc exhibits a great increase after a critical heat treatment time. When the heat treatment time increases, one obtains an increase in Hc after a shorter heat treatment time. This jump of Hc was explained by a transition from the superparamagnetic state to normal state of the single domain nanoparticles. The occurrence of an agglomerated structure composed of magnetically interacting ultrafine crystallites also contributes to the increase of Hc.The heat treatment determines a reduced grain growth due to the internal stress generated by R ions. With increasing R content the σs and σr decrease due to the dissolution of R ions into the hexaferrite lattice. We believe that by selecting the time and temperature of the heat treatment, microstructure and magnetic properties suitable for magnetic recording media application can be obtained. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)