Tuning of perpendicular exchange bias for magnetic memory applications

AbstractPerpendicular magnetic anisotropy (PMA) ferromagnetic CoFeB with dual MgO interfaces is an attractive material system for realizing magnetic memory applications that require highly efficient, high speed current-induced magnetic switching. Using this structure, a sub-nanometer CoFeB layer has the potential to simultaneously exhibit efficient, high speed switching in accordance with the conservation of spin angular momentum, and high thermal stability owing to the enhanced interfacial PMA that arises from the two CoFeB-MgO interfaces. However, the difficulty in attaining PMA in ultrathin CoFeB layers has imposed the use of thicker CoFeB layers which are incompatible with high speed requirements. In this work, we succeeded in depositing a functional CoFeB layer as thin as five monolayers between two MgO interfaces using magnetron sputtering. Remarkably, the insertion of Mg within the CoFeB gave rise to an ultrathin CoFeB layer with large anisotropy, high saturation magnetization, and good annealing stability to temperatures upwards of 400 °C. When combined with a low resistance-area product MgO tunnel barrier, ultrathin CoFeB magnetic tunnel junctions (MTJs) demonstrate switching voltages below 500 mV at speeds as fast as 1 ns in 30 nm devices, thus opening a new realm of high speed and highly efficient nonvolatile memory applications.

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Observation of giant exchange bias effect in Ni-Mn-Ti all-d-metal Heusler alloy

Journal of Physics Condensed Matter ◽

10.1088/1361-648x/ac3e9b ◽

2021 ◽

Author(s):

Saheli Samanta ◽

Subrata Ghosh ◽

Kalyan Mandal

Keyword(s):

Exchange Bias ◽

Heusler Alloy ◽

Magnetic Relaxation ◽

Training Effect ◽

Magnetic Memory ◽

Relaxation Processes ◽

Bias Effect ◽

Exchange Bias Effect ◽

Intrinsic Nature ◽

Unidirectional Anisotropy

Abstract We report a giant exchange bias (EB) field of about 3.68 KOe during field cooled process in all-d-metal Ni40(FeCo)4Mn36Ti20 Heusler alloy. The study of magnetic memory effect and isothermal magnetic relaxation processes suggest that the giant EB field arises due to the possible coexistence of antiferromagnetic (AFM) and ferromagnetic (FM) phase exchange interaction in the studied system at temperatures below 35 K. Furthermore, the temperature and cooling field dependence of EB effect are analyzed which are related to the change in unidirectional anisotropy at FM/AFM interface. The study of a well-established training effect confirms the intrinsic nature of the observed EB behavior. This result will open up a new way towards the development of EB materials considering all-d-metal Heusler alloy systems.

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STRUCTURAL AND MAGNETIC PROPERTIES OF THE THIN FILM OF COBALT NITRIDE

Surface Review and Letters ◽

10.1142/s0218625x14500814 ◽

2014 ◽

Vol 21 (06) ◽

pp. 1450081 ◽

Cited By ~ 2

Author(s):

ZOHRA NAZIR KAYANI ◽

SAIRA RIAZ ◽

SHAHZAD NASEEM

Keyword(s):

Magnetic Properties ◽

Sol Gel ◽

Magnetic Memory ◽

Vibrating Sample Magnetometer ◽

Orthorhombic Structure ◽

X Ray ◽

Cu Substrates ◽

Gel Technique ◽

Structural And Magnetic Properties ◽

Memory Applications

Cobalt nitride has been prepared and studied for magnetic memory applications. Sol–gel technique is used to prepare thin films of cobalt nitride. The films were deposited onto Cu substrates by spin coating at 3000 rpm for 30 s. The films were then air dried and heated at 300°C for 120 min. As-deposited and heated samples were characterized for their structural and magnetic properties using X-ray diffractometer (XRD) and vibrating sample magnetometer (VSM) techniques. The grain size was in the range of 22.7–30.10 nm. Their surface was studied by scanning electron microscopy (SEM). Orthorhombic structure can be seen in SEM micrographs. This orthorhombic structure is also confirmed by XRD.

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Characterization and Modeling of Spin-Transfer Torque (STT) Magnetic Memory for Computing Applications

Special Topics in Information Technology - SpringerBriefs in Applied Sciences and Technology ◽

10.1007/978-3-030-62476-7_5 ◽

2021 ◽

pp. 51-62

Author(s):

Roberto Carboni

Keyword(s):

Computer Architecture ◽

Random Number Generator ◽

Data Communication ◽

Spin Transfer Torque ◽

Spin Transfer ◽

Magnetic Memory ◽

Von Neumann ◽

Stochastic Computing ◽

Performance Limitation ◽

Memory Applications

AbstractWith the ubiquitous diffusion of mobile computing and Internet of Things (IoT), the amount of data exchanged and processed over the internet is increasing every day, demanding secure data communication/storage and new computing primitives. Although computing systems based on microelectronics steadily improved over the past 50 years thanks to the aggressive technological scaling, their improvement is now hindered by excessive power consumption and inherent performance limitation associated to the conventional computer architecture (von Neumann bottleneck). In this scenario, emerging memory technologies are gaining interest thanks to their non-volatility and low power/fast operation. In this chapter, experimental characterization and modeling of spin-transfer torque magnetic memory (STT-MRAM) are presented, with particular focus on cycling endurance and switching variability, which both present a challenge towards STT-based memory applications. Then, the switching variability in STT-MRAM is exploited for hardware security and computing primitives, such as true-random number generator (TRNG) and stochastic spiking neuron for neuromorphic and stochastic computing.

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Distinctive exchange bias and unusual memory effects in magnetically compensated Pr0.75Gd0.25ScGe

Journal of Materials Chemistry C ◽

10.1039/d0tc05087c ◽

2021 ◽

Vol 9 (1) ◽

pp. 181-188

Author(s):

Tyler Del Rose ◽

Arjun K. Pathak ◽

Yaroslav Mudryk ◽

Vitalij K. Pecharsky

Keyword(s):

Exchange Bias ◽

Memory Effects ◽

Magnetic Memory ◽

Magnetic Compensation ◽

Layered Lattice

Inter-lanthanide interactions in a distinctly layered lattice lead to magnetic compensation, exchange bias, and magnetic memory effects.

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Investigation of ferroelectrics using conventional and in situ electron microscopy

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100170669 ◽

1994 ◽

Vol 52 ◽

pp. 586-587

Author(s):

V. Saikumar ◽

H. M. Chan ◽

M. P. Harmer

Keyword(s):

Nonvolatile Memory ◽

Ferroelectric Materials ◽

Gate Insulator ◽

Sensors And Actuators ◽

In Situ Electron Microscopy ◽

Ferroelectric Domains ◽

Domain Boundaries ◽

Domain Interactions ◽

Memory Applications

In recent years, there has been a growing interest in the application of ferroelectric thin films for nonvolatile memory applications and as a gate insulator in DRAM structures. In addition, bulk ferroelectric materials are also widely used as components in electronic circuits and find numerous applications in sensors and actuators. To a large extent, the performance of ferroelectric materials are governed by the ferroelectric domains (with dimensions in the micron to sub-micron range) and the switching of domains in the presence of an applied field. Conventional TEM studies of ferroelectric domains structures, in conjunction with in-situ studies of the domain interactions can aid in explaining the behavior of ferroelectric materials, while providing some answers to the mechanisms and processes that influence the performance of ferroelectric materials. A few examples from bulk and thin film ferroelectric materials studied using the TEM are discussed below.Figure 1 shows micrographs of ferroelectric domains obtained from undoped and Fe-doped BaTiO3 single crystals. The domain boundaries have been identified as 90° domains with the boundaries parallel to <011>.

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