Wihuri Physical Laboratory, Department of Physics and Astronomy, University of Turku, FI-20014 Turku, Finland.
J Phys Condens Matter. 2011 Sep 28;23(38):386005. doi: 10.1088/0953-8984/23/38/386005. Epub 2011 Sep 13.
Optimization of thin films of small bandwidth manganite, Pr(1-x)Ca(x)MnO3 (for x = 0.1), and their magnetic properties are investigated. Using different pulsed laser deposition (PLD) conditions, several films were deposited from the stoichiometric target material on SrTiO3 (001) substrate and their thorough structural and magnetic characterizations were carried out using x-ray diffraction, atomic force microscopy, x-ray photoelectron spectroscopy (XPS), SQUID magnetometry and ac susceptibility measurements. A systematic investigation shows that irrespective of the growth temperature (between 550 and 750 °C), all the as-deposited films have twin boundaries and magnetic double phases. Post-annealing in partial or full oxygen pressure removes the extra phase and the twin boundaries. Zero-field-cooled magnetization data show an antiferromagnetic to paramagnetic transition at around 100 K whereas the field-cooled magnetization data exhibit a paramagnetic to ferromagnetic transition close to 120 K. However, depending on the oxygen treatments, the saturation magnetization and Curie temperature of the films change significantly. Redistribution of oxygen vacancies due to annealing treatments leading to a change in ratio of Mn3+ and Mn4+ in the films is observed from XPS measurements. Low temperature (below 100 K) dc magnetization of these films shows metamagnetic transition, high coercivity and irreversibility magnetizations, indicating the presence of a spin-glass phase at low temperature. The frequency dependent shift in spin-glass freezing temperature from ac susceptibility measurement confirms the coexistence of spin-glass and ferromagnetic phases in these samples at low temperature.
对具有较窄带宽的锰氧化物薄膜 Pr(1-x)Ca(x)MnO3（其中 x = 0.1）进行了优化，并研究了其磁性。使用不同的脉冲激光沉积（PLD）条件，从化学计量靶材在 SrTiO3（001）衬底上沉积了几种薄膜，并使用 X 射线衍射、原子力显微镜、X 射线光电子能谱（XPS）、超导量子干涉磁强计和交流磁化率测量对其进行了全面的结构和磁性表征。系统的研究表明，无论生长温度（550 到 750°C 之间）如何，所有沉积的薄膜都具有孪晶界和双相磁性。在部分或全部氧压下退火可以消除多余的相和孪晶界。零场冷却磁化数据显示在 100 K 左右有反铁磁到顺磁转变，而场冷却磁化数据显示在 120 K 左右有顺磁到铁磁转变。然而，根据氧处理条件的不同，薄膜的饱和磁化强度和居里温度有显著变化。XPS 测量表明，退火处理会导致氧空位重新分布，从而导致薄膜中 Mn3+和 Mn4+的比例发生变化。这些薄膜在低温（低于 100 K）下的直流磁化显示出了顺磁到铁磁转变、高矫顽力和不可逆磁化，表明在低温下存在自旋玻璃相。从交流磁化率测量得出的自旋玻璃冻结温度的频率相关偏移证实了这些样品在低温下自旋玻璃相和铁磁相共存。
