| As the development of science and technology, scientific research workers has been gradually in-depth to explore microscopic material world. Electron:an integral part of the atom, also caused the interest of some scientists when most of the scientists put the attention on the inside of nucleus. Last century, as the result of the research and controlling of the charge which is one of the electron’s degree of freedom, the microelectronics rise up sharply. Since the end of the 20th century, more attention have been put on the other degree of freedom of electron:spin. Thus, a new branch of science: spintronics can rapid development. As the development of spintronics, the generation, injection and control of the spin current has been known well by scientists, more and more kinds of spintronics devices which work on the basis of spin current have been used in the daily life.At the year of 1988, the Giant Magnetoresistance (GMR) was discovered, which made the magnetic recording technology obtained the chance of leap-forward development. In the past three decades, the limit of the traditional magnetic recording hard disk in recording density, reading and writing speed was constantly refreshed. In the year of 2012, Seagate promote the recording density of the magnetic recording hard disk up to 1 Tb/inch2. In order to improve the recording density of the magnetic recording hard disk, more and more magnetic storage materials with big coercivity has been used into the magnetic recording hard disk. As a result, it’s become more and more difficult to turn over the magnetic moment of the memory cell using the traditional hard disk read head, thus, we can’t finish the reading-writing operation normally. When the development of the traditional magnetic recording went into dilemma, a lot of new type magnetic recording technology were invented. As a member of these new type magnetic recording technology, the Microwave Assisted Magnetic Recording (MAMR) infliction an assist microwave with a certain amount of power on the memory cell during the reading-writing operation, the magnetic moment of the memory cell will adsorb the energy of the microwave, which will make its magnetic moment can be turn over by a smaller outside magnetic field. In order to send high frequency microwave by a nano-meter hard disk read head, a new spintronics device was put forward:the Spin Torque Nano-Oscillator (STNO) which works with on the basis of Magnetic Tunnel Junction (MTJ). The working principle of the STNO is the Spin Transfer Torque (STT) in the magnetic tunnel junction, when current across the MTJ along the direction from the pinning layer to the free layer, the magnetic moment of the free layer will precess under the drive of the polarization current, high frequency microwave will send out during the magnetic moment precession.Process the MTJ used in the spin torque nano-oscillator is one of the work of this paper. In this research subject, we designed a new type of spin torque nano-oscillator on the basis of CoFeB/MgO/CoFeB magnetic tunnel junction. Using the micro magnetic simulation software, we simulated the working condition of the spin torque nano-oscillator, in the simulation we observed the condition during which high frequency microwave was send out continual. We designed and optimized a completed set of micro processing technology to make the CoFeB/MgO/CoFeB magnetic tunnel junction, on the basis of the UV lithography technology and argon ion etching technology. Using the micro processing technology, we processed the CoFeB/MgO/CoFeB magnetic tunnel junction successfully, Lift-off technology was also used during the processing. By optimizing the sputtering condition of CoFeB and MgO, we reduce the thickness of MgO under to 1nm, in which a TMR ratio of 9% was observed in a MTJ with the area of 10μm×10μm.As the development of the spintronics, some research subject such as Spin Hall Magnetoresistance (SMR), Inverse Spin Hall Effect (ISHE), Spin Seebeck Effect (SSE), Spin Pumping Effect at all, has attracted the attention of the scientists. During the research on these subjects, a type of ferromagnetic insulation material with small FMR line width and low Gilbert damping coefficient was essential. However, YIG can meet all this requirement, and it’s the only ferromagnetic insulation material with low Gilbert damping coefficient. In the year of 2014, Mingzhong. Wu et al deposited signal crystal YIG nano-meter film on GGG (111) use PLD and magnetron sputtering respectively, which have the FMR line width for only 6.9 Oe. The YIG nano-meter film deposited with the magnetron sputtering even have an Gilbert damping coefficient of (8.74 ± 0.33)×10-5, which is the lowest reported Gilbert damping coefficient until now. In the limit of the quality of the YIG target and the sputtering difficulty, only a handful of people can deposited signal crystal YIG nano-meter film using magnetron sputtering in our country.The other important work of this paper is the sintering of YIG target and the sputtering of single crystal YIG nano-meter film. Firstly, different from the solid-phase reaction, we use the fusion nitric acid to sintering the YIG target. A 2-inch high purity target with the saturation magnetization of 26.2 emu/g was sintered successfully, in which the XRD peak show the polycrystalline structure.Using the sintered YIG target, we sputtered signal crystal YIG nano-meter film on GGG (111) successfully, without the heat of the substrate and the Oxygen reaction sputtering. In the signal crystal YIG nano-meter film, we observed an FMR line-width of 11.66 Oe at 9.7 GHz, the FMR field of 9.7 GHz is 2751 Oe, the saturation magnetization is 4πMs=1514 G, the gyromagnetic ratio is as small as|γ|= 2.827 MHz/Oe, the Gilbert damping coefficient is as low as a=6.98×10-5 and the surface roughness is as small as RMS=0.069nm. All of these parameters which can represent the high quality of the YIG film were observed in the same sample. The most narrow line width we can observed at 9.7 GHz is 8.07 Oe. |
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