Three dimensional magnetic abacus memory

Scientific Reports Nature Publishing Group 4 (2014) 6109-

S Zhang, J Zhang, A Baker, S Wang, G Yu, T Hesjedal

Stacking nonvolatile memory cells into a three-dimensional matrix represents a powerful solution for the future of magnetic memory. However, it is technologically challenging to access the data in the storage medium if large numbers of bits are stacked on top of each other. Here we introduce a new type of multilevel, nonvolatile magnetic memory concept, the magnetic abacus. Instead of storing information in individual magnetic layers, thereby having to read out each magnetic layer separately, the magnetic abacus adopts a new encoding scheme. It is inspired by the idea of second quantisation, dealing with the memory state of the entire stack simultaneously. Direct read operations are implemented by measuring the artificially engineered ‘quantised’ Hall voltage, each representing a count of the spin-up and spin-down layers in the stack. This new memory system further allows for both flexible scaling of the system and fast communication among cells. The magnetic abacus provides a promising approach for future nonvolatile 3D magnetic random access memory.

Modelling ferromagnetic resonance in magnetic multilayers: Exchange coupling and demagnetisation-driven effects


AA Baker, CS Davies, AI Figueroa, LR Shelford, G van der Laan, T Hesjedal

Pressure-induced polar phases in multiferroic delafossite CuFeO2

PHYSICAL REVIEW B 89 (2014) ARTN 220403

N Terada, DD Khalyavin, P Manuel, T Osakabe, PG Radaelli, H Kitazawa

The roles of chirality and polarity in novel multiferroics: MnSb2O6 and Cu3Nb2O8


R Johnson, L Chapon, K Cao, P Manuel, A Bombardi, S Nair, S Cheong, P Radaelli

Magnetic ordering in Cr-doped Bi₂Se₃ thin films

Europhysics Letters: a letters journal exploring the frontiers of physics European Physical Society 107 (2014) 57009-57009

L Collins-Mcintyre, SE Harrison, P Schoenherr, N-J Steinke, C Kinane, T Charlton, D Alba-Veneroa, A Phusp, A Kellock, SSP Parkin, JS Harris, S Langridge, G van der Laan, T Hesjedal

We report the structural and magnetic study of Cr-doped Bi2Se3 thin films using x-ray diffraction (XRD), magnetometry and polarized neutron reflectometry (PNR). Epitaxial layers were grown on c-plane sapphire by molecular beam epitaxy in a two-step process. High-resolution XRD shows the exceptionally high crystalline quality of the doped films with no parasitic phases up to a Cr concentration of 12% (in % of the Bi sites occupied by substitutional Cr). The magnetic moment, measured by SQUID magnetometry, was found to be ${\sim}2.1\ \mu_\text{B}$ per Cr ion. The magnetic hysteresis curve shows an open loop with a coercive field of ${\sim}10\ \text{mT}$ . The ferromagnetic transition temperature was determined to be $8.5\ \text{K}$ analyzing the magnetization-temperature gradient. PNR shows the film to be homogeneously ferromagnetic with no enhanced magnetism near the surface or interface.

Comparison of Au and TiO2 based catalysts for the synthesis of chalcogenide nanowires


P Schoenherr, D Prabhakaran, W Jones, N Dimitratos, M Bowker, T Hesjedal

Vapour-liquid-solid growth of ternary Bi2Se2Te nanowires.

Nanoscale research letters 9 (2014) 127-

P Schönherr, LJ Collins-McIntyre, S Zhang, P Kusch, S Reich, T Giles, D Daisenberger, D Prabhakaran, T Hesjedal

: High-density growth of single-crystalline Bi2Se2Te nanowires was achieved via the vapour-liquid-solid process. The stoichiometry of samples grown at various substrate temperatures is precisely determined based on energy-dispersive X-ray spectroscopy, X-ray diffraction, and Raman spectroscopy on individual nanowires. We discuss the growth mechanism and present insights into the catalyst-precursor interaction.

Engineering of Bi2Se3 nanowires by laser cutting


P Schoenherr, AA Baker, P Kusch, S Reich, T Hesjedal

Policy: Crystallography needs a governing body.

Nature 505 (2014) 607-609

PG Radaelli

Realization of a three-dimensional spin-anisotropic harmonic honeycomb iridate.

Nature communications 5 (2014) 4203-4203

KA Modic, TE Smidt, I Kimchi, NP Breznay, A Biffin, S Choi, RD Johnson, R Coldea, P Watkins-Curry, GT McCandless, JY Chan, F Gandara, Z Islam, A Vishwanath, A Shekhter, RD McDonald, JG Analytis

Spin and orbital quantum numbers play a key role in the physics of Mott insulators, but in most systems they are connected only indirectly--via the Pauli exclusion principle and the Coulomb interaction. Iridium-based oxides (iridates) introduce strong spin-orbit coupling directly, such that these numbers become entwined together and the Mott physics attains a strong orbital character. In the layered honeycomb iridates this is thought to generate highly spin-anisotropic magnetic interactions, coupling the spin to a given spatial direction of exchange and leading to strongly frustrated magnetism. Here we report a new iridate structure that has the same local connectivity as the layered honeycomb and exhibits striking evidence for highly spin-anisotropic exchange. The basic structural units of this material suggest that a new family of three-dimensional structures could exist, the 'harmonic honeycomb' iridates, of which the present compound is the first example.

Magnetic and ferroelectric orderings in multiferroic alpha-NaFeO2

PHYSICAL REVIEW B 89 (2014) ARTN 184421

N Terada, DD Khalyavin, JM Perez-Mato, P Manuel, D Prabhakaran, A Daoud-Aladine, PG Radaelli, HS Suzuki, H Kitazawa

Crystallography needs a governing body

Nature 505 (2014) 607-609

PG Radaelli

Diffraction Studies of Multiferroics


RD Johnson, PG Radaelli

Magnetic phase diagram and ordered ground state of GdMn2O5 multiferroic studied by x-ray magnetic scattering


C Vecchini, A Bombardi, LC Chapon, N Lee, PG Radaelli, S-W Cheong, IOP

Study of Gd-doped Bi2Te3 thin films: Molecular beam epitaxy growth and magnetic properties

Journal of Applied Physics 115 (2014) 2

SE Harrison, LJ Collins-McIntyre, S Li, AA Baker, LR Shelford, Y Huo, A Pushp, SSP Parkin, JS Harris, E Arenholz, G van der Laan, T Hesjedal

CaBaCo4O7: A ferrimagnetic pyroelectric

PHYSICAL REVIEW B 90 (2014) ARTN 045129

RD Johnson, K Cao, F Giustino, PG Radaelli

First-principles study of multiferroic RbFe(MoO4)(2)

PHYSICAL REVIEW B 90 (2014) ARTN 024402

K Cao, RD Johnson, F Giustino, PG Radaelli, G-C Guo, L He

Magnetically induced femtoscale strain modulations in HoMn2O5

PHYSICAL REVIEW B 89 (2014) ARTN 125114

C Vecchini, A Bombardi, LC Chapon, G Beutier, PG Radaelli, S Park, S-W Cheong

Erratum: X-ray imaging and multiferroic coupling of cycloidal magnetic domains in ferroelectric monodomain BiFeO<inf>3</inf> (Physical Review Letters (2013) 110 (217206))

Physical Review Letters 111 (2013)

RD Johnson, P Barone, A Bombardi, RJ Bean, S Picozzi, PG Radaelli, YS Oh, SW Cheong, LC Chapon

Coherent magnon and acoustic phonon dynamics in tetragonal and rare-earth-doped BiFeO<inf>3</inf> multiferroic thin films

Physical Review B - Condensed Matter and Materials Physics 88 (2013)

KI Doig, F Aguesse, AK Axelsson, NM Alford, S Nawaz, VR Palkar, SPP Jones, RD Johnson, RA Synowicki, J Lloyd-Hughes

Coherent magnons and acoustic phonons were impulsively excited and probed in thin films of the room temperature multiferroic Bi1-x-yDy xLayFeO3 using femtosecond laser pulses. The elastic moduli of rhombohedral, tetragonal, and rare-earth doped BiFeO 3 were determined from acoustic-mode frequencies in conjunction with spectroscopic ellipsometry. A weak ferromagnetic order, induced alternately by magnetization in the growth direction or by tetragonality, created a magnon oscillation at 75 GHz, indicative of a Dzyaloshinskii-Moriya interaction energy of 0.31 meV. © 2013 American Physical Society.