Spin transfer switching in TbCoFe∕CoFeB∕MgO∕CoFeB∕TbCoFe magnetic tunnel junctions with perpendicular magnetic anisotropy

Abstract

Spin transfer (ST) switching in the TbCoFe∕CoFeB∕MgO∕CoFeB∕TbCoFe magnetic tunnel junction (MTJ) was studied. The TbCoFe∕CoFeB free layer with a large coercive field of 1.2kOe and a large thermal stability factor of 107 at room temperature was switched by a 100ns pulse current with a current density of 4.7MA∕cm2. This is the first report of ST switching in a MTJ with perpendicular magnetic anisotropy. The temperature dependence of the coercive field was also investigated to estimate the magnetic anisotropy in the case of rising temperature due to the Joule heating effect. The measured coercive field at 87°C, which was the simulated temperature during the switching pulse current, was about 0.34kOe. The ratio of the switching current density to the coercive field under the switching current in the MTJ with the TbCoFe∕CoFeB free layer is smaller than that in a typical MTJ with an in-plane magnetized CoFeB free layer. This result indicates that a MTJ with perpendicular magnetic anisotropy is advantageous for realizing low switching current magnetoresistive random access memory.

Reducing the switching current with a Gilbert damping constant in nanomagnets with perpendicular anisotropy

“…1,2 This technique can be used to develop non-volatile memory with both high-speed magnetization switching and low power consumption, e.g., spin-torque magnetoresistive random access memory (spin-RAM). There have been many theoretical reports on magnetization switching 3,4 and experimental studies of in-plane [5][6][7] and out-of-plane [8][9][10][11][12][13][14][15] magnetization magnets. To realize high-density spin-RAM, a low-magnetization switching current is required for the writing process, and a high thermal stability factor (D) is required to retain the information record.…”

“…Magnetic materials with perpendicular magnetic anisotropy can meet the above requirements. [8][9][10][11][12][13][14][15] These materials can reduce the switching current (I sw ) and sustain the magnetization direction at room temperature, even for device sizes of less than a few tens of nanometers. [8][9][10] In a practical spin-RAM device with size of several tens of nanometers, currents of <100 lA are required, and the main memory and cache memory must be accessed within timeframes of <10 ns and <1 ns, respectively.…”

“…[8][9][10][11][12][13][14][15] These materials can reduce the switching current (I sw ) and sustain the magnetization direction at room temperature, even for device sizes of less than a few tens of nanometers. [8][9][10] In a practical spin-RAM device with size of several tens of nanometers, currents of <100 lA are required, and the main memory and cache memory must be accessed within timeframes of <10 ns and <1 ns, respectively. 16,17 Theoretically, the switching current for spin-transfer torque reversal of the out-of-plane magnetization using a current of infinite duration (DC current) in a thin-film geometry is given by 5,7,8,10 …”

Computing with spins and magnets

“…Role of the third magnetic layer (below Ru) is to cancel the stray field of the reference layer on the storage layer. Depending on the parallel (P) or anti-parallel (AP) orientation of the magnetization of the free and fixed layers, the resistance 26,27 ( Figure 1a) of the MTJ can change by more than 100%. 27 In addition, the free layer in the MTJ can be electrically switched in a sub-200 ps time scale.…”

Tunable perpendicular magnetic anisotropy in GdFeCo amorphous films

“…For devices, it is preferable to use a single film layer with perpendicular magnetic anisotropy instead of multilayer in order to avoid complicated fabrication process and decrease the total thickness of the devices. One well-known candidate is amorphous rare-earth transition-metal (RE-TM) thin films with strong perpendicular magnetic anisotropy [2,3,4]. Amorphous GdFeCo films have been known to have a low saturation magnetization, preventing magnetization curling at the film edge.…”