Conductive Atomic Force Microscopy of Small Magnetic Tunnel Junctions With Interface Anisotropy

Patterning of sub-50 nm perpendicular CoFeB/MgO-based magnetic tunnel junctions

“…Although the lithography process is different from that of the EBL samples, the ion beam etching step was the same and we expect the edge profile of the dots to be representative of that of the EBL-patterned samples. The TMR was in the range of 20%, consistent with [12], which shows that TMR decreased with increasing sample bias, from approximately 100% at low bias to just below 20% at 900 mV bias.…”

“…The minor loops give H i =160, 65 and 45 Oe and H c,soft =10, 95 and 95 Oe for diameters of 60, 125 and 250 nm respectively. The bottom harder CoFeB layer magnetization can only be reversed in a major loop [12] so the effect of the soft layer field on the hard layer cannot be determined from H c1 . Smaller devices, 45 nm diameter, showed a resistance that was consistent with their area but the 600 Oe field available from the magnet in the cAFM was insufficient to switch both magnetic layers.…”

“…Conductive AFM measurements were done using a RHK UHV350 with R9 controller in contact mode and an Asylum Research Cypher AFM tool. Conductive probes were fabricated by coating commercial non-conducting probes with nominally 200 nm of Pt on a Ti adhesion layer using a process detailed elsewhere [11,12]. Commercial conductive probes, Rocky Mountain Nanotechnology RMN 12Pt300B, were also used.…”

Logic circuit prototypes for three-terminal magnetic tunnel junctions with mobile domain walls

“…Figure 2a shows an example of a device acting as an inverter, which can be used to do a two-input NAND operation, with parallel MTJ resistance R P =23.7 Ω, antiparallel MTJ resistance R AP =25.7 Ω, wire resistance R w =1.18 kΩ and tunnel magnetoresistance TMR =( R AP − R P )/ R P × 100=8.4% (ref. 25 ). Initialization with H I sets the MTJ initially in a parallel state (bit 1), with the DW on the left as in Fig.…”

Magnetic reversal and thermal stability of CoFeB perpendicular magnetic tunnel junction arrays patterned by block copolymer lithography

“…The growth [4][5][6][7] , the physical origin of interfacial anisotropy 8 , and voltage-controlled magnetic properties [9][10][11] of p-MTJs have been extensively characterized. Scaling and switching behavior have been investigated in p-MTJ devices with diameters ranging from 11 nm to 500 nm [12][13][14][15][16] , and the effective anisotropy has been estimated by analyzing telegraph noise while measuring TMR using conductive atomic force microscopy 17 .…”