Fabrication of Curie point written solid state magnetic memories

居里点写入固态磁存储器的制作

基本信息

批准号：
13555092
负责人：
TSUNASHIMA Shigeru
金额：
$ 8.7万
依托单位：
Nagoya University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2001
资助国家：
日本
起止时间：
2001 至 2003
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-13555092/
关键词：
solid state magnetic momery MRAM spin tunneling junction non-volatile memory Blocking temperature exchanae anisotropy spin polarized transport

项目摘要

Micropatterned amorphous films for thermomagnetic recording, TMR films using amorphous alloy layers, exchange biased films, and thermomagnetic recording process were investigated.(1) TbFe amorphous alloy films were prepared by rf magnetron sputtering, and microfabricated by focused ion beam (FIB) and conventional photolithography methods. Switching of the magnetization of TbFe elements was confirmed after current pulses which give rise to Joule heat in the elements. The current density necessary for the switching was found to decrease with decreasing the element size, and the 0.5μm squared element was found to be switched by applying the current density as small as 1.6 x 10^6 A/cm^2. In addition, tunnel junctions including TbFe amorphous alloy layer was found to exhibit sufficiently large magneto resistance ratio.(2) NiFe/Mnlr exchange biased films were microfabricated by FIB and their magnetic domain structures were observed by magnetic force microscopy (MFM). The easy direction of the NiFe/Mnlr elements lay in the film plane, and for such in-plane elements having 1 : 1 aspect ratio, it is difficult to obtain sigle domain state. Thus, the perpendicular magnetized elements such as TbFe were found to be effective to accomplish single domain state if the elements have 1 : 1 aspect ratio.(3) Simulation of thermomagnetic recording process was carried out, and the simulation was used to obtain material parameters which are necessary for recording of domains smaller than 100 nm. For the recording of domains smaller than 50 nm on an RE-rich TbFeCo medium, the increase of coercivity, which might be realized by controlling the microstructure of the TbFeCo film, was found to be needed.

研究了用于热磁记录的微图案非晶薄膜、非晶合金层TMR薄膜、交换偏置薄膜和热磁记录工艺。(1)采用射频磁控溅射技术制备了TbFe非晶合金薄膜，并采用聚焦离子束(FIB)和常规技术进行了微加工。光刻方法在电流脉冲后确认了 TbFe 元件的磁化强度，该电流脉冲在元件中产生焦耳热所需的电流密度。研究发现开关随着元件尺寸的减小而降低，并且发现通过施加小至 1.6 x 10^6 A/cm^2 的电流密度即可开关 0.5μm 的方形元件。此外，隧道结包括 TbFe 非晶态。 (2)利用FIB微加工NiFe/Mnlr交换偏置薄膜并通过磁力显微镜观察其磁畴结构(MFM) NiFe/Mnlr 元素的易磁化方向位于薄膜平面内，对于具有 1:1 长宽比的面内元素，很难获得单畴状态，因此，诸如垂直磁化的元素。发现TbFe在元素长径比为1:1的情况下可有效实现单畴态。(3)对热磁记录过程进行了模拟,并通过模拟获得了记录所需的材料参数。为了在富含稀土的 TbFeCo 介质上记录小于 50 nm 的磁畴，需要增加矫顽力，这可以通过控制 TbFeCo 薄膜的微观结构来实现。