Full voltage manipulation of the resistance of a magnetic tunnel junction

One of the motivations for multiferroics research is to find an energy-efficient solution to spintronic applications, such as the solely electrical control of magnetic tunnel junctions. Here, we integrate spintronics and multiferroics by depositing MgO-based magnetic tunnel junctions on ferroelectric substrate. We fabricate two pairs of electrodes on the ferroelectric substrate to generate localized strain by applying voltage. This voltage-generated localized strain has the ability to modify the magnetic anisotropy of the free layer effectively. By sequentially applying voltages to these two pairs of electrodes, we successively and unidirectionally rotate the magnetization of the free layer in the magnetic tunnel junctions to complete reversible 180° magnetization switching. Thus, we accomplish a giant nonvolatile solely electrical switchable high/low resistance in magnetic tunnel junctions at room temperature without the aid of a magnetic field. Our results are important for exploring voltage control of magnetism and low-power spintronic devices.

Download Full-text

Detection of Sub-Nano-Tesla Magnetic Field by Integrated Magnetic Tunnel Junctions with Bottom Synthetic Antiferro-Coupled Free Layer

Japanese Journal of Applied Physics ◽

10.7567/jjap.52.04cm07 ◽

2013 ◽

Vol 52 (4S) ◽

pp. 04CM07 ◽

Cited By ~ 9

Author(s):

Kosuke Fujiwara ◽

Mikihiko Oogane ◽

Takuo Nishikawa ◽

Hiroshi Naganuma ◽

Yasuo Ando

Keyword(s):

Magnetic Field ◽

Tunnel Junctions ◽

Magnetic Tunnel Junctions ◽

Free Layer

Download Full-text

Fabrication of Magnetic Tunnel Junctions with a Synthetic Ferrimagnetic Free Layer for Magnetic Field Sensor Applications

Japanese Journal of Applied Physics ◽

10.7567/jjap.50.013001 ◽

2011 ◽

Vol 50 (1R) ◽

pp. 013001 ◽

Cited By ~ 4

Author(s):

Kousuke Fujiwara ◽

Mikihiko Oogane ◽

Futoyoshi Kou ◽

Daisuke Watanabe ◽

Hiroshi Naganuma ◽

...

Keyword(s):

Magnetic Field ◽

Tunnel Junctions ◽

Magnetic Tunnel Junctions ◽

Magnetic Field Sensor ◽

Free Layer ◽

Sensor Applications ◽

Field Sensor

Download Full-text

Fabrication of Magnetic Tunnel Junctions with a Synthetic Ferrimagnetic Free Layer for Magnetic Field Sensor Applications

Japanese Journal of Applied Physics ◽

10.1143/jjap.50.013001 ◽

2011 ◽

Vol 50 ◽

pp. 013001 ◽

Cited By ~ 5

Author(s):

Kousuke Fujiwara ◽

Mikihiko Oogane ◽

Futoyoshi Kou ◽

Daisuke Watanabe ◽

Hiroshi Naganuma ◽

...

Keyword(s):

Magnetic Field ◽

Tunnel Junctions ◽

Magnetic Tunnel Junctions ◽

Magnetic Field Sensor ◽

Free Layer ◽

Sensor Applications ◽

Field Sensor

Download Full-text

Highly Charged Ion Modified Magnetic Tunnel Junctions

MRS Proceedings ◽

10.1557/proc-0960-n08-02 ◽

2006 ◽

Vol 960 ◽

Cited By ~ 1

Author(s):

Holger Grube ◽

J. M. Pomeroy ◽

A. C. Perrella ◽

J. D. Gillaspy

Keyword(s):

Magnetic Field ◽

Giant Magnetoresistance ◽

Room Temperature ◽

Tunnel Junctions ◽

Magnetic Tunnel Junctions ◽

Oxide Thickness ◽

Present Measurement ◽

Field Sensor ◽

Highly Charged Ion ◽

Charged Ions

ABSTRACTWe have used highly charged ions (HCIs) such as Xe44+ to modify ultrathin aluminum oxide barriers in magnetic tunnel junctions (MTJs) in order to controllably adjust their electrical properties independently of oxide thickness. We have reduced the resistance area (RA) product of our MTJ devices by up to three orders of magnitude down to our present measurement uncertainty limit of 30 Ω·μm2 by varying the HCI dose. Preliminary experiments indicate that HCI modified Co/Al2O3/Co MTJs have a reduced magnetoresistance (MR) of ≈ 1% at room temperature as compared to ≈ 10% for undosed devices. The goal of this effort is to fabricate a magnetic field sensor in current-perpendicular-to-plane (CPP) geometry with an RA optimized for hard drive read heads. This is an improvement over presently demonstrated CPP architectures based on giant magnetoresistance or tunnel junctions, whose RAs are either to low or too high.

Download Full-text

PATTERNED NANOSCALE MAGNETIC TUNNEL JUNCTIONS WITH DIFFERENT GEOMETRICAL STRUCTURES

SPIN ◽

10.1142/s2010324711000094 ◽

2011 ◽

Vol 01 (01) ◽

pp. 109-114 ◽

Cited By ~ 4

Author(s):

Z. C. WEN ◽

Y. WANG ◽

G. Q. YU ◽

H. X. WEI ◽

B. S. ZHANG ◽

...

Keyword(s):

Magnetic Field ◽

Critical Current Density ◽

Tunnel Junctions ◽

Ring Width ◽

Magnetic Tunnel Junctions ◽

Geometrical Shape ◽

Magnetization Switching ◽

Geometrical Structures ◽

Spintronic Devices ◽

Shape Dependence

In this paper, patterned nanoscale magnetic tunnel junctions (MTJs) with different geometrical structures, including nanodisk (ND), nanoellipse (NE), nanoring (NR) and nanoelliptical ring (NER) with the scale of around 100nm and ring width of around 30nm, were fabricated, respectively. The geometrical-shape dependence of magnetic field-driven and current-induced magnetization switching (CIMS) were studied in the nanoscale magnetic tunnel junctions (MTJs). The NER-MTJs showed robust magnetization switching and low critical current density of CIMS, comparing with other geometrical-shaped MTJs. This may be due to the different distribution of current-induced Oersted field in different geometrical structures, which plays an assisted role in CIMS. The present experiments indicate that NER-MTJs may be one of the promising candidates for the cells of high-density and low-consumption spintronic devices.

Download Full-text

Fabrication of Magnetic Tunnel Junctions with Synthetic Coupled Free Layer for Highly Sensitive Magnetic Field Sensor Devices

10.7567/ssdm.2014.ps-12-12 ◽

2014 ◽

Author(s):

D. Kato ◽

M. Oogane ◽

K. Fujiwara ◽

T. Nishikawa ◽

H. Naganuma ◽

...

Keyword(s):

Magnetic Field ◽

Tunnel Junctions ◽

Magnetic Tunnel Junctions ◽

Magnetic Field Sensor ◽

Free Layer ◽

Highly Sensitive ◽

Sensor Devices ◽

Field Sensor

Download Full-text

Magnetization Reversal by Spin-Polarized Current in Magnetic Tunnel Junctions with MgO Barriers

Advances in Science and Technology ◽

10.4028/www.scientific.net/ast.45.2633 ◽

2006 ◽

Vol 45 ◽

pp. 2633-2639

Author(s):

Hitoshi Kubota ◽

A. Fukushima ◽

Y. Ootani ◽

S. Yuasa ◽

K. Ando ◽

...

Keyword(s):

Thermal Stability ◽

Layer Thickness ◽

Magnetization Reversal ◽

Tunnel Junctions ◽

Magnetic Tunnel Junctions ◽

Magnetic Tunnel Junction ◽

Free Layer ◽

Switching Model ◽

Switching Current ◽

Experimental Values

Co-Fe-B/MgO/Co-Fe-B magnetic tunnel junctions were fabricated using UHV magnetron sputtering. Magnetoresistance and spin-transfer switching properties were investigated as a function of Co-Fe-B free layer thickness, between 1.5 nm and 3 nm. The intrinsic switching current and the thermal stability were derived from the pulse duration dependence of the switching current, analyzed based on the thermally activated switching model. Both switching currents, corresponding to parallel (P) to antiparallel (AP) (Ic0 +) and AP to P (Ic0 –) magnetization reversal, were found to be roughly proportional to the free layer thickness. The averaged intrinsic switching current density Jc0 av = (Ic0 +–Ic0 –)/(2A) (where A is the cell area) was in the range of 1–2×107 A/cm2. The experimental values of Jc0 ± agreed with theoretical values, determined taking into account the spintransfer efficiency for the case of magnetic tunnel junction. The thermal stability of the P and AP states was different, but roughly proportional to the free layer thickness in both cases. We attribute this difference to a disparity in the net magnetic field acting on the free layer magnetization in the P and AP states. The average of the thermal stability in the two states varied from 30 to 60 when the free layer thickness was increased. According to our findings, to guarantee the non-volatility of an MRAM device for about 10 years, the Co-Fe-B free layer should be thicker than 2 nm.

Download Full-text