Koutzarova Tatyana, Kolev Svetoslav, Krezhov Kiril, Georgieva Borislava, Kovacheva Daniela, Ghelev Chavdar, Vertruyen Benedicte, Boschini Frederic, Mahmoud Abdelfattah, Tran Lan Maria, Zaleski Andrzej
Institute of Electronics, Bulgarian Academy of Sciences, 72 Tsarigradsko Chaussee, 1784 Sofia, Bulgaria.
Institute of General and Inorganic Chemistry, Bulgarian Academy of Sciences, Acad. Georgi Bonchev Str., bld. 11, 1113 Sofia, Bulgaria.
Materials (Basel). 2019 Apr 30;12(9):1414. doi: 10.3390/ma12091414.
BaMgCoFeO was prepared in powder form by sonochemical co-precipitation and examined by X-ray diffraction, Mössbauer spectroscopy and magnetization measurements. Careful XRD data analyses revealed the Y-type hexaferrite structure as an almost pure phase with a very small amount of CoFeO as an impurity phase (about 1.4%). No substantial changes were observed in the unit cell parameters of BaMgCoFeO in comparison with the unsubstituted compound. The Mössbauer parameters for BaMgCoFeO were close to those previously found (within the limits of uncertainty) for undoped BaMgFeO. Isomer shifts (0.27-0.38 mm/s) typical for high-spin Fe in various environments were evaluated and no ferrous Fe form was observed. However, despite the indicated lack of changes in the iron oxidation state, the cationic substitution resulted in a significant increase in the magnetization and in a modification of the thermomagnetic curves. The magnetization values at 50 kOe were 34.5 emu/g at 4.2 K and 30.5 emu/g at 300 K. The zero-field-cooled (ZFC) and field-cooled (FC) magnetization curves were measured in magnetic fields of 50 Oe, 100 Oe, 500 Oe and 1000 Oe, and revealed the presence of two magnetic phase transitions. Both transitions are shifted to higher temperatures compared to the undoped compound, while the ferrimagnetic arrangement at room temperature is transformed to a helical spin order at about 195 K, which is considered to be a prerequisite for the material to exhibit multiferroic properties.
通过声化学共沉淀法制备了粉末状的BaMgCoFeO，并通过X射线衍射、穆斯堡尔光谱和磁化测量进行了研究。仔细的XRD数据分析表明，Y型六铁氧体结构几乎为纯相，含有极少量的CoFeO作为杂质相（约1.4%）。与未取代的化合物相比，BaMgCoFeO的晶胞参数没有观察到实质性变化。BaMgCoFeO的穆斯堡尔参数与先前在未掺杂的BaMgFeO中发现的参数相近（在不确定度范围内）。评估了各种环境中高自旋Fe典型的同质异能位移（0.27 - 0.38 mm/s），未观察到亚铁Fe的形式。然而，尽管铁氧化态没有明显变化，但阳离子取代导致磁化强度显著增加，并改变了热磁曲线。在50 kOe下，4.2 K时的磁化值为34.5 emu/g，300 K时为30.5 emu/g。在50 Oe、100 Oe、500 Oe和1000 Oe的磁场中测量了零场冷却（ZFC）和场冷却（FC）磁化曲线，结果表明存在两个磁相变。与未掺杂的化合物相比，这两个相变都向更高温度移动，而室温下的亚铁磁排列在约195 K时转变为螺旋自旋序，这被认为是该材料表现出多铁性的先决条件。
