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Articles 1 - 13 of 13
Full-Text Articles in Physical Sciences and Mathematics
Electrically Controlled Exchange Bias For Spintronic Applications, Christian Binek, A. Hochstrat, X. Chen, P. Borisov, W. Kleeman, B. Doudin
Electrically Controlled Exchange Bias For Spintronic Applications, Christian Binek, A. Hochstrat, X. Chen, P. Borisov, W. Kleeman, B. Doudin
Christian Binek
Exchange coupling between a magnetoelectric (111)-oriented Cr2O3 single crystal and a CoPt multilayer with perpendicular anisotropy exhibits an exchange bias field proportional to the applied axial electric field. Extrapolation from bulk to thin film magnetoelectric pinning system suggests promising spintronic applications due to coupling between the electric field-controlled magnetization and the magnetization of a neighbor ferromagnetic layer. Pure voltage control of magnetic configurations of tunneling magnetoresistance spin valves is an attractive alternative to current-induced magnetization switching. ©2005 American Institute of Physics
Freezing Field Dependance Of The Exchange Bias In Uniaxial Fef2-Copt Heterosystems With Perpendicular Anisotropy, Christian Binek
Freezing Field Dependance Of The Exchange Bias In Uniaxial Fef2-Copt Heterosystems With Perpendicular Anisotropy, Christian Binek
Christian Binek
The exchange bias effect is measured for the first time in FeF2–CoPt heterosystems with perpendicular anisotropy. The exchange previous field exhibits a strong dependence on the axial previous freezing field. This behavior is explained in terms of the microscopic spin structure at the interface, which is established on cooling to below TN. We calculate the dependence of the spin structure on the previous freezing field within the framework of an Ising model. It takes into account the Zeeman energy as well as an antiferromagnetic exchange coupling between the adjacent layers at the interface.
Isothermal Low-Field Tuning Of Exchange Bias In Epitaxial Fe/Cr2o3/Fe, S. Sahoo, T. Mukherjee, K. Belashchenko, Christian Binek
Isothermal Low-Field Tuning Of Exchange Bias In Epitaxial Fe/Cr2o3/Fe, S. Sahoo, T. Mukherjee, K. Belashchenko, Christian Binek
Christian Binek
Moderate dc magnetic fields of less than 1 T allow tuning the exchange bias in an epitaxially grown Fe 10 nm/Cr2O3 2.7 nm/Fe 10 nm trilayer between negative and positive bias fields. Remarkably, this tunable exchange bias is observed at least up to 395 K which exceeds the Néel temperature of bulk Cr2O3 (307 K). The presence of spontaneous exchange bias and the absence of training effects at room temperature suggest the existence of stable interface moments independent of antiferromagnetic long range order in Cr2O3. Furthermore, the coercivity remains constant, independent of the exchange bias field. In contrast, large training …
Temperature Dependence Of The Training Effect In Exchange Coupled Ferromagnetic Bilayers, S. Polisetty, Sarbeswar Sahoo, A. Berger, Christian Binek
Temperature Dependence Of The Training Effect In Exchange Coupled Ferromagnetic Bilayers, S. Polisetty, Sarbeswar Sahoo, A. Berger, Christian Binek
Christian Binek
The temperature dependence of the training effect is studied in an exchange coupled thin-film bilayer composed of a hard ferromagnetic pinning (CoPtCrB) layer in proximity of a soft ferromagnetic pinned (CoCr) layer. Interlayer exchange shifts the hysteresis loops of the soft layer along the magnetic-field axis. This shift is quantified by the bias field in far reaching analogy to the exchange bias field of conventional antiferromagnetic/ferromagnetic heterostructures. A ferromagnetic domain state induced in the hard layer experiences aging very similar to the training behavior of the antiferromagnetic domain state in conventional exchange bias systems. Training originates from changes in the …
Dilution-Induced Enhancement Of The Blocking Temperature In Exchange-Bias Heterosystems, Xi Chen, Christian Binek, A. Hochstrat, W. Kleeman
Dilution-Induced Enhancement Of The Blocking Temperature In Exchange-Bias Heterosystems, Xi Chen, Christian Binek, A. Hochstrat, W. Kleeman
Christian Binek
The temperature dependence of the exchange bias field is investigated by superconducting quantum interference device magnetometry in Fe1-xZnxF2(110)/Fe14 nm/Ag35 nm, x=0.4. Its blocking temperature exhibits a significant enhancement with respect to the global ordering temperature TN=46.9 K, of the bulk antiferromagnet Fe0.6Zn0.4F2. The enhancement is attributed to fluctuations of the diamagnetic dilution which creates clusters on all length scales having a Zn dilution of 0<~x<~1. While the infinite clusters give rise to the well-known Griffiths phase, finite clusters also provoke a local enhancement of the exchange bias. The temperature dependence of the integral exchange bias effect is modeled by averaging all local contributions of the antiferromagnetic surface magnetization which exhibit a surface critical behavior.
Magnetic Relaxation Phenomena In The Superspin-Glass System [Co80Fe20/Al2O3]10, S. Sahoo, O. Petracic, Christian Binek, W. Kleemann, J. B. Sousa, S. Cardoso, P. P. Freitas
Magnetic Relaxation Phenomena In The Superspin-Glass System [Co80Fe20/Al2O3]10, S. Sahoo, O. Petracic, Christian Binek, W. Kleemann, J. B. Sousa, S. Cardoso, P. P. Freitas
Christian Binek
Relaxation and temperature cycles of thermoremanent magnetization, MTRM, in the superspin-glass phase of [Co80Fe20 (0.9 nm)/Al2O3 (3 nm)] 10 have been investigated. The relaxation of MTRM exhibits ageing phenomena. In negative temperature cycles for temperature steps larger than 1 K the magnetic state is retrieved (memory effect) on returning to the measurement temperature. This property is independent of the application of a field step during intermediate cooling. In positive temperature cycles the relaxation is suppressed after temporary heating. The observations are discussed in the light of both the droplet and the hierarchical picture.
Metamagnetic Domains And Dynamic Fluctuations In Febr2, O. Petracic, Christian Binek, W. Kleeman
Metamagnetic Domains And Dynamic Fluctuations In Febr2, O. Petracic, Christian Binek, W. Kleeman
Christian Binek
The mixed phase and the regime of non-critical fluctuations of the magnetic phase diagram of FeBr2 is investigated by SQUID susceptometry and light diffraction techniques. The experiments seem to evidence instability of the tricritical point as conjectured recently. The observation of stripe domains and light diffraction below and above Tm = 4.6 K and the virtual continuation of the phase transition line to above Tm are in agreement with the occurrence of a critical endpoint at Tm and of a bicritical endpoint at T > Tm. ©1997 American Institute of Physics.
Quenching Of The Exchange Bias Training In Fe/Cr2o3/Fe Trilayer, S. Sahoo, Christian Binek
Quenching Of The Exchange Bias Training In Fe/Cr2o3/Fe Trilayer, S. Sahoo, Christian Binek
Christian Binek
Exchange bias (EB) and its associated training effects are studied in an epitaxial Fe(10 nm)/Cr2O3(2.7 nm)/Fe(10 nm) trilayer heterostructure grown by molecular beam epitaxy. The EB decreases linearly with increasing temperature from T = 5 K to T = 50 K. It changes sign and becomes positive within 50 K < T < 200 K, finally changing back to regular EB for T<200K up to the highest measured temperature of T = 395 K. Remarkably, the latter is far above the bulk Néel temperature TN = 307 K. EB training effects occur only at 5 K < T < 50 K. We show …
Magnetic States Of Discontinuous Co80fe20al2o3 Multilayers, Christian Binek
Magnetic States Of Discontinuous Co80fe20al2o3 Multilayers, Christian Binek
Christian Binek
Discontinuous metal–insulator multilayers [Co80Fe20(t)/Al2O3(3 nm)]n were studied by SQUID magnetometry and AC susceptometry. CoFe forms ferromagnetic particles in the Al2O3 matrix. In this paper, we focus on the field dependence of the AC susceptibility of samples with t=1.3 nm. We find strong evidence for transitions from a superpara- to a superferromagnetic and, finally, to a reentrant superspin glass previous state.
Nonadiabatic Heat-Capacity Measurements Using A Superconducting Quantum Interference Device Magnetometer, A.I. Kharkovski, Christian Binek, W. Kleeman
Nonadiabatic Heat-Capacity Measurements Using A Superconducting Quantum Interference Device Magnetometer, A.I. Kharkovski, Christian Binek, W. Kleeman
Christian Binek
Nonadiabatic measurements of the heat capacity involving sample-inherent thermometry are proposed. The method is realized with superconducting quantum interference device magnetometry and applied to FeBr2 single crystals by using the magnetization for both thermometry and relaxation calorimetry. When heating with a step pulse of laser light, the magnetization relaxes on a characteristic time scale Ί = RC, where C is the heat capacity and R is the heat resistance between the sample and the bath. R is independently determined from the temperature dependence of the magnetic moment measured with and without stationary light irradiation. ©2000 American Institute of Physics.
Robust Isothermal Electric Control Of Exchange Bias At Room Temperature, Xi He, Yi Wang, Christian Binek, Peter Dowben
Robust Isothermal Electric Control Of Exchange Bias At Room Temperature, Xi He, Yi Wang, Christian Binek, Peter Dowben
Christian Binek
Voltage-controlled spin electronics is crucial for continued progress in information technology. It aims at reduced power consumption, increased integration density and enhanced functionality where non-volatile memory is combined with highspeed logical processing. Promising spintronic device concepts use the electric control of interface and surface magnetization. From the combination of magnetometry, spin-polarized photoemission spectroscopy, symmetry arguments and first-principles calculations, we show that the (0001) surface of magnetoelectric Cr2O3 has a roughness-insensitive, electrically switchable magnetization. Using a ferromagnetic Pd/Co multilayer deposited on the (0001) surface of a Cr2O3 single crystal, we achieve reversible, room-temperature isothermal switching of the exchange-bias field between positive …
Domain Wall Relaxation, Creep, Sliding, And Switching In Superferromagnetic Discontinuous Co80Fe20/Al2O3 Multilayers, X. Chen, O. Sichelschmidt, W. Kleeman, Christian Binek, J.B. Sousa, S. Cardoso, P.P. Freitas
Domain Wall Relaxation, Creep, Sliding, And Switching In Superferromagnetic Discontinuous Co80Fe20/Al2O3 Multilayers, X. Chen, O. Sichelschmidt, W. Kleeman, Christian Binek, J.B. Sousa, S. Cardoso, P.P. Freitas
Christian Binek
The ac susceptibility of a superferromagnetic discontinuous multilayer [Co80Fe20(1.4 nm)/ Al2O3(3 nm)]10 is measured as a function of temperature, frequency, and field amplitude and compared to static and dynamic hysteresis loops. Its properties are successfully mapped onto the predicted [T. Nattermann, V. Pokrovsky, and V. M. Vinokur, Phys. Rev. Lett. 87, 197005 (2001).] dynamical phase transitions, which link the relaxation, creep, sliding, and switching regimes of pinned domain walls.
Electrically Controlled Magnetism, Christian Binek, Xi He, Yi Wang, S. Sahoo
Electrically Controlled Magnetism, Christian Binek, Xi He, Yi Wang, S. Sahoo
Christian Binek
Manipulation of magnetically ordered states by electrical means is a promising approach towards novel spintronics devices. We report on the electric control of surface magnetism in Cr2O3 thin films and uniaxial anisotropy in ferroelectric/ferromagnetic heterostructures, respectively. Artificial magnetoelectricity is realized in a BaTiO3/Fe heterostructure. Here, thermally induced coercivity changes of the Fe hysteresis loop are used to derive the stress imposed by the ferroelectric BaTiO3 substrate on the adjacent Fe film. Electrically induced coercivity changes give rise to a giant magnetoelectric susceptibility in the vicinity of the magnetic coercive field.