基于电子顺磁共振的锶铁氧体磁特性研究

为了研究配料、温度、氧环境和掺杂等条件对锶铁氧体的磁性能的影响问题, 利用溶胶-凝胶法制备了锶铁氧体粉末, 建立了一种基于电子顺磁共振技术研究锶铁氧体粉末的磁特性的方法. 用电子顺磁共振波谱仪对烧结后的产物进行测试发现: 400 ℃预烧下, 锶铁摩尔比为1:9时, 中间产物顺磁相α-Fe₂O₃含量最多, 高于400 ℃时其含量减少, 亚铁磁相增加, 并确定最佳煅烧温度介于800-900 ℃. 这是由于外磁场和其他磁场综合作用产生亚铁磁相, 进而产生较强的磁矩相互作用所致. 结合工业实际应用, 发现缺氧退火环境下, 顺磁相α-Fe₂O₃含量较大, 不利于亚铁磁相生成; X-射线衍射(XRD)表征结果表明: 除了少量杂相, 其余均为顺磁相和亚铁磁相; 电子顺磁共振谱和XRD 谱检测结果综合表明, 锶铁摩尔比为1:9时, 最终产物的顺磁相含量最少, 亚铁磁相含量最多, 磁性最强; 毫特斯拉计的剩磁检测结果也证实了上述结果. 掺杂实验发现镧离子占锶镧总摩尔数的20% 至30% 时, 能够有效降低顺磁相的产生, 增强最终产物的亚铁磁性.

Study on magnetic properties of strontium ferrite based on the technology of electron paramagnetic resonance

In order to study how the ingredient, sintering temperature, oxygen, doping and other conditions affect magnetic properties of strontium ferrite powder, a strontium ferrite powder is prepared by sol-gel method, and a new method of studying magnetic properties of strontium ferrite powder based on an electron paramagnetic resonance (EPR) is established in this paper. The sintered samples are tested by electron paramagnetic resonance spectrometer. Results show that α-Fe₂O₃, a paramagnetic intermediate, is most compared with other ratios under calcined at 400 ℃ and the strontium iron mole ratio of 1:9; while at the other temperatures it decreases and the ferromagnetic phase increases; the optimum calcination temperature is between 800 ℃ and 900 ℃. These facts are caused by both external magnetic field and other magnetic fields, thus resulting in some new stronger magnetic moment interactions. Results also show that a large quantity of paramagnetic α-Fe₂O₃ is found under hypoxic annealing environment, which is not conducible to generating the ferrimagnetic phase; X-ray diffraction (XRD) analysis shows that the others are paramagnetic and ferrimagnetic phase except a bit of other phases; both EPR spectra and XRD spectra show that the paramagnetic phase is least, and ferrimagnetic phase is most in the sintering sample when strontium iron mole ratio is 1:9, so the sample owns the strongest magnetism. The sample remanence experiment by milli-tesla meter also confirms these results. It is also found that paramagnetic phase can effectively decrease and ferrimagnetism is enhanced when samples are doped by lanthanum ion accounting for 20%-30% of the total number of moles of strontium lanthanum.