通过原子层沉积法生长的多晶铋铁氧体薄膜的磁性

Magnetic Properties of Polycrystalline Bismuth Ferrite Thin Films Grown by Atomic Layer Deposition.

作者信息

Jalkanen Pasi, Tuboltsev Vladimir, Marchand Benoît, Savin Alexander, Puttaswamy Manjunath, Vehkamäki Marko, Mizohata Kenichiro, Kemell Marianna, Hatanpää Timo, Rogozin Valentin, Räisänen Jyrki, Ritala Mikko, Leskelä Markku

机构信息

†Department of Physics, Division of Materials Physics, University of Helsinki, P.O. Box 43, FI-00014, Helsinki, Finland.

‡School of Science, O.V. Lounasmaa Laboratory, Aalto University, P.O. Box 15100, FI-00076, Espoo, Finland.

出版信息

J Phys Chem Lett. 2014 Dec 18;5(24):4319-23. doi: 10.1021/jz502285f. Epub 2014 Dec 4.

DOI:10.1021/jz502285f

PMID:26273981

Abstract

The atomic layer deposition (ALD) method was applied to grow thin polycrystalline BiFeO3 (BFO) films on Pt/SiO2/Si substrates. The 50 nm thick films were found to exhibit high resistivity, good morphological integrity, and homogeneity achieved by the applied ALD technique. Magnetic characterization revealed saturated magnetization of 25 emu/cm(3) with temperature-dependent coercivity varying from 5 to 530 Oe within the temperature range from 300 to 2 K. Magnetism observed in the films was found to change gradually from ferromagnetic spin ordering to pinned magnetic domain interactions mixed with weak spin-glass-like behavior of magnetically frustrated antiferromagnetic/ferromagnetic (AFM-FM) spin ordering depending on the temperature and magnitude of the applied magnetic field. Antiferromagnetic order of spin cycloids was broken in polycrystalline films by crystal sizes smaller than the cycloid length (∼60 nm). Uncompensated spincycloids and magnetic domain walls were found to be the cause of the high magnetization of the BFO films.

摘要

采用原子层沉积（ALD）方法在Pt/SiO2/Si衬底上生长了多晶BiFeO3（BFO）薄膜。发现通过应用ALD技术制备的50nm厚薄膜具有高电阻率、良好的形态完整性和均匀性。磁性表征显示，在300至2K的温度范围内，饱和磁化强度为25emu/cm³，矫顽力随温度变化，从5Oe到530Oe不等。发现薄膜中观察到的磁性会根据温度和外加磁场强度，从铁磁自旋有序逐渐转变为与磁阻挫反铁磁/铁磁（AFM-FM）自旋有序的弱自旋玻璃状行为混合的钉扎磁畴相互作用。在多晶薄膜中，小于摆线长度（约60nm）的晶体尺寸破坏了自旋摆线的反铁磁序。未补偿的自旋摆线和磁畴壁被认为是BFO薄膜高磁化强度的原因。