Northrop Grumman Systems Corporation

Microsoft Technology Licensing, LLC

Thomas F Ambrose

Melissa G Loving

James Matthew Murduck

Nicholas David Rizzo

Michael Manuel Fitelson

Eric C Gingrich

Alastair Charlie Fisher

Kurt Edward Dietrich

Timothy Richard Barbour

James M Murduck

A buffer layer can be used to smooth the surface roughness of a galvanic contact layer (e.g., of niobium) in an electronic device, the buffer layer being made of a stack of at least four (e.g., six) layers of a face-centered cubic (FCC) crystal structure material, such as copper, the at least four FCC material layers alternating with at least three layers of a body-centered cubic (BCC) crystal structure material, such as niobium, wherein each of the FCC material layers and BCC material layers is between about five and about ten angstroms thick. The buffer layer can provide the smoothing while still maintaining desirable transport properties of a device in which the buffer layer is used, such as a magnetic Josephson junction, and magnetics of an overlying magnetic layer in the device, thereby permitting for improved magnetic Josephson junctions (MJJs) and thus improved superconducting memory arrays and other devices.

Repeating alternating multilayer buffer layer

One example includes a magnetic Josephson junction (MJJ) system. The system includes a first superconducting material layer and a second superconducting material layer each configured respectively as a galvanic contacts. The system also includes a ferrimagnetic material layer arranged between the first and second superconducting material layers and that is configured to exhibit a fixed net magnetic moment at a predetermined operating temperature of the MJJ system. The system also includes a ferromagnetic material layer arranged between the first and second superconducting material layers and that is configured to exhibit a variable magnetic orientation in response to an applied magnetic field. The MJJ system can be configured to store a binary logical value based on a direction of the variable magnetic orientation of the ferromagnetic material layer. The system further includes a spacer layer arranged between the ferromagnetic and the ferrimagnetic material layers.

Magnetic Josephson junction system

A memory device includes a memory stack formed on a substrate to program skyrmions within at least one layer of the stack. The skyrmions represent logic states of the memory device. The memory stack further includes a top and bottom electrode to receive electrical current from an external source and to provide the electrical current to the memory stack. A free layer stores a logic state of the skyrmions in response to the electrical current. A Dzyaloshinskii-Moriya (DM) Interaction (DMI) layer in contact with the free layer induces skyrmions in the free layer. A tunnel barrier is interactive with the DMI layer to facilitate detection of the logic state of the skyrmions in response to a read current. At least one fixed magnetic (FM) layer is positioned within the memory stack to facilitate programming of the skyrmions within the free layer in response to the electrical current.

Skyrmion stack memory device

A magnetic Josephson junction (MJJ) device having a ferrimagnetic/ferromagnetic (FIM/FM) exchange-biased bilayer used as the magnetic hard layer improves switching performance by effectively sharpening the hysteresis curve of the device, thereby reducing error rate when the device is used in a Josephson magnetic random access memory (JMRAM) memory cell. Thus, the materials and devices described herein can be used to build a new type of MJJ, termed a ferrimagnetic Josephson junction (FIMJJ), for use in JMRAM, to construct a robust and reliable cryogenic computer memory that can be used for high-speed superconducting computing, e.g., with clock speeds in the microwave frequency range.

Ferrimagnetic/ferromagnetic exchange bilayers for use as a fixed magnetic layer in a superconducting-based memory device

A sealed container having gloves attached thereto is provided as part of a physical properties measuring system (PPMS). The PPMS includes a sealed pressurized portion that is pressurized with a gas to purge out air from inside the sealed pressurized portion to reduce water vapor inside the sealed pressurized portion below a water vapor threshold. The system further includes a cryogenic tank having a cryostat disposed therein. The cryogenic tank contains a cryogenic liquid cooled to a cryogenic temperature. Test samples are placed inside the sealed pressurized portion in preparation of measuring physical properties of the test samples. One of the test samples is immersed in the cryogenic liquid to measure the physical properties. The test sample is removed from the cryogenic liquid and is exchanged for another test sample inside the sealed pressurized portion to prevent ice formation inside the cryostat.

Physical properties measurement system

A memory cell is provided that comprises a first superconductor electrode, a second superconductor electrode, and a magnetic Josephson junction (MJJ) stack disposed between the first superconductor electrode and the second superconductor electrode. The MJJ stack includes a magnetic reference layer and a magnetic storage layer. The memory cell further comprises a magnetically stabilizing structure disposed between the MJJ stack and the second superconductor electrode, wherein the magnetic stabilizing structure magnetically couples with the magnetic reference layer to strengthen the fixed state of the magnetic reference layer.

Magnetically stabilized magnetic Josephson junction memory cell

Superconducting circuits and memories that use a magnetic Josephson junction (MJJ) device as a pi inverter are disclosed. The MJJ device includes superconducting layers configured to allow a flow of a supercurrent through the MJJ device. The MJJ device further includes a magnetic layer arranged between the superconducting layers, where the magnetic layer has an associated magnetization direction, and where the first state of the MJJ device corresponds to a zero-phase of a supercurrent flowing through the MJJ device and the second state of the MJJ device corresponds to a &#x3c0;-phase of the supercurrent flowing through the MJJ device. In response to an application of a magnetic field, without any change in the magnetization direction of the magnetic layer, the MJJ device is configured to switch from the first state to the second state responsive to a change in a phase of the supercurrent.

Using a magnetic Josephson junction device as a pi inverter

Magnetic Josephson junction driven flux-biased superconductor memory cell and methods are provided. A memory cell may include a magnetic Josephson junction (MJJ) superconducting quantum interference device (SQUID) comprising a first MJJ device and a second MJJ device, arranged in parallel to each other, where the MJJ SQUID is configured to generate a first flux-bias or a second flux-bias, where the first flux-bias corresponds to a first direction of current flow in the MJJ SQUID and the second flux-bias corresponds to a second direction of current flow in the MJJ SQUID. The memory cell may further include a superconducting metal-based superconducting quantum interference device (SQUID) including a first Josephson junction (JJ) and a second JJ, arranged in parallel to each other, where each of the first JJ and the second JJ has a critical current responsive to any flux-bias generated by the MJJ SQUID.

Magnetic josephson junction driven flux-biased superconductor memory cell and methods

Examples described in this disclosure relate to a memory cell having a magnetic Josephson junction device with a doped magnetic layer. In one example, a memory cell including a magnetic Josephson junction (MJJ) device is provided. The MJJ device may include at least a first layer formed above a second layer and a third layer formed below the second layer, where the first layer is a free magnetic layer, the second layer is a non-magnetic layer, where the third layer is a fixed magnetic layer. The free magnetic layer may comprise a magnetic alloy doped with at least one of Vanadium, Zirconium, Molybdenum, or Hafnium, and the fixed magnetic layer may comprise an un-doped second magnetic alloy.

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Crownsville, MD, United States of America

Thomas F Ambrose