不同气氛沉积和后退火处理的HfOx〈2薄膜的弱铁磁性

无磁性掺杂HfO2薄膜的室温弱铁磁性是2004年发现的一种不能用传统固体铁磁理论释的奇特磁现.本文用射频磁控溅射方法在不同气中制备和后退火HfOx薄膜样品,对比研究气对其室温弱铁磁性的影响.物析表明,室温沉积在蓝石衬底上的HfOx薄膜为部晶的单斜多晶薄膜,且存在一定程度的氧失配.室温磁性测量果显示HfOx〈2多晶薄膜具有典型的弱铁磁性磁化曲,且饱和磁矩具有各异性.对比实验果表明,缺氧气（纯氩或氩氮混合气）中沉积薄膜的和磁矩略大于富氧气（氩氧混合气）中沉积薄膜的和磁矩.缺氧气（纯氮和高真空）中后退火处理后,薄膜饱和磁矩随着退火温度的升高而增大;而纯氧气中后退火处理后,薄膜和磁矩大幅减小.沉积和后退火气中氧含量的高低对薄膜和磁矩的显影响表明氧空位是HfOx〈2薄膜弱铁磁性的要来源之一.

Weak ferromagnetism of HfOx films deposited by sputtering in different depositing/annealing ambient

Weak ferromagnetism of un-doped HfOx films is a bit new magnetic phenomenon discovered in 2004, challenging people＇s understanding on traditional solid magnetism theories. In this work, we report the effects of sputtering/ annealing ambient on the weak ferromagnetic properties of HfOx films deposited on C-cut sapphire substrate by radio frequency （rf） magnetron sputtering, and discuss its possible origins. Its microstructures and magnetic properties are characterized by using X-ray diffraction, X-ray photoelectron spectrum and vibrating-sample-magnetometer, respectively. It is demonstrated that the as-deposited HfOx film is oxygen defective and has monoclinic crystalline structure. Its magnetization curves indicate a typical ferromagnetic behavior and show a visible anisotropy. The saturated magnetic moment （M） of HfOx films deposited in oxygen-defective ambient （pure Ar or Ar-N2 mixture ambient） is larger than that deposited in the Ar-O2 mixture ambient. When annealed in N2 atmosphere or high vacuum （-3.0×10 4 Pa）, the saturated M of samples increases as the annealing temperature increases. On the contrary, after annealed in pure O2 atmosphere, the saturated M of samples greatly decreases. The significant effects of oxygen content of sputtering/annealing ambient on the ferromagnetic properties of HfOx films imply that oxygen vacancies are one of main origins of the weak ferromagnetism.