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 Bias (3)
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Articles 1  14 of 14
FullText Articles in Physics
DilutionInduced Enhancement Of The Blocking Temperature In ExchangeBias Heterosystems, Xi Chen, Christian Binek, A. Hochstrat, Wolfgang Kleemann
DilutionInduced Enhancement Of The Blocking Temperature In ExchangeBias Heterosystems, Xi Chen, Christian Binek, A. Hochstrat, Wolfgang Kleemann
Christian Binek Publications
The temperature dependence of the exchange bias field is investigated by superconducting quantum interference device magnetometry in Fe_{1x}Zn_{x}F2(110)/Fe14 nm/Ag35 nm, x=0.4. Its blocking temperature exhibits a significant enhancement with respect to the global ordering temperature T_{N}=46.9 K, of the bulk antiferromagnet Fe_{0.6}Zn_{0.4}F_{2}. 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 wellknown 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.
Exchange Bias In Fef20Copt Heterosystems With Perpendicular Anisotropy, Christian Binek
Exchange Bias In Fef20Copt Heterosystems With Perpendicular Anisotropy, Christian Binek
Christian Binek Publications
The previous exchange bias effect is measured in heterosystems with perpendicular anisotropy consisting of Co/Pt multilayers on top of the (0 0 1) face of a previous FeF2 single crystal. The resulting previous exchange field HE exhibits a strong dependence on temperature and the axial freezing field, HF. Within the framework of an Isingtype model, the HE vs. T as well as the HE vs. HF data are explained in terms of the microscopic spin structure at the interface.
Ac Susceptibility Studies Of Discontinuous Co80fe20al2o3 Multilayers, Christian Binek
Ac Susceptibility Studies Of Discontinuous Co80fe20al2o3 Multilayers, Christian Binek
Christian Binek Publications
Discontinuous metal–insulator multilayers [Co80Fe20(t)/Al2O3(3 nm)]10 are prepared by ionbeam sputtering and investigated by SQUID magnetometry and previous AC susceptometry. For 1.0lessthanorequals, slanttlessthanorequals, slant1.6 nm, two coexisting subsystems of dipolar coupled nanoparticles are encountered. While a spinglasslike freezing particulate fraction dominates at t=1.0 nm, a percolating dipolar ferromagnetic fraction becomes increasingly important at higher nominal thickness of t.
Transverse Magnetism Of The Diluted Antiferromagnet Fe1Xmgxbr2 (X=0.15), Christian Binek
Transverse Magnetism Of The Diluted Antiferromagnet Fe1Xmgxbr2 (X=0.15), Christian Binek
Christian Binek Publications
Neutron diffraction and magnetization measurements of the diluted crystal Fe1−xMgxBr2 (xnot, vert, similar0.15) were performed. Successive phase transitions at zero applied field at TN1not, vert, similar12 K and TN2not, vert, similar10 K were found. A previous transverse term ferromagnetic moment was detected just below TN2.
Magnetic States Of Discontinuous Co80fe20al2o3 Multilayers, Christian Binek
Magnetic States Of Discontinuous Co80fe20al2o3 Multilayers, Christian Binek
Christian Binek Publications
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.
Exchange Bias In Fe0.6zn0.4f2 Heterostructures, Christian Binek
Exchange Bias In Fe0.6zn0.4f2 Heterostructures, Christian Binek
Christian Binek Publications
The previous exchange bias field, He, is measured in Fe0.6Zn0.4F2/Fe heterosystems prepared from Fe layers of 14 and 5 nm thickness which are deposited on top of the compensated (1 1 0) surface of the antiferromagnet. Deviations from a linear dependence of He on the magnetization of the Fe layer are attributed to ferromagnetic domains. Moreover, piezomagnetism and its influence on He are evidenced.
Domain State Susceptibility In Fecl2/CoptHeterostructures, Christian Binek
Domain State Susceptibility In Fecl2/CoptHeterostructures, Christian Binek
Christian Binek Publications
Magnetic heterostructures with perpendicular anisotropy consisting of antiferromagnetic (111)oriented FeCl2 single crystals and thin ferromagnetic CoPtmultilayers are investigated by acsusceptometry after cooling in various axial magnetic fields to below the Néel temperature. The freezing process drives the system into a metastable antiferromagnetic domain state which gives rise to a huge excess contribution to the complex parallel susceptibility on heating in zero magnetic field. Its glow curvelike temperature dependence is modeled within the framework of a simple analytical approach. It involves the susceptibility of thermally activated clusters originating from antiferromagnetic stacking faults as well as the contribution of pairs of ...
OffDiagonal ExchangeInduced Transverse And FieldInduced SpinFlop Order In The Diluted Metamagnet Fe_{0.85}Mg_{0.15}Br_{2}, Wolfgang Kleeman, H. Aruga Katori, T. Kato, Christian Binek, K. Katsumata
OffDiagonal ExchangeInduced Transverse And FieldInduced SpinFlop Order In The Diluted Metamagnet Fe0.85Mg0.15Br2, Wolfgang Kleeman, H. Aruga Katori, T. Kato, Christian Binek, K. Katsumata
Christian Binek Publications
Specific heat and Faraday rotation magnetometry were used to determine the axial magnetic phase diagram of the dilute hexagonal antiferromagnet Fe_{0.85}Mg_{0.15}Br_{2}. In contrast to metamagnetic pure FeBr_{2}, the firstorder line of transverse phase transitions, H1(T), is disconnected with the antiferrotoparamagnetic phase line H_{c}(T) and extends down to H_{t}=0 at T_{t}≈8.7 . This is attributed to symmetric offdiagonal exchange in the presence of structural disorder. Moreover, a spinflop phase emerges beyond H_{c}(T) up to a bicritical point (T_{b}≈9.3 , μ_{o}H ...
Exchange Bias In A Generalized MeiklejohnBean Approach, Christian Binek
Exchange Bias In A Generalized MeiklejohnBean Approach, Christian Binek
Christian Binek Publications
A generalized Meiklejohn–Bean model is considered in order to derive an analytic expression for the dependence of the previous exchange bias term field on the layer thickness involved in ferromagnetic/antiferromagnetic heterosystems, on the orientation of the applied magnetic field with respect to the magnetic easy axes and on the quenched magnetization MAF of the antiferromagnetic pinning layer. While MAF is a wellknown feature of fieldcooled dilute antiferromagnets, it seems to occur quite generally also in pure AF pinning substrates. The new analytic expressions are successfully compared with recent experimental results and Monte Carlo investigations.
YangLee Edge Singularities From Experimental High Field Magnetization Data, Christian Binek
YangLee Edge Singularities From Experimental High Field Magnetization Data, Christian Binek
Christian Binek Publications
The isothermal magnetization m(H) of the metamagnet FeCl2 is measured in axial magnetic fields 0≤µ0Ha≤12 T at temperatures 34≤T≤53 K above the Néel temperature, where the system is essentially a twodimensional Ising ferromagnet. The analysis of the data indicates experimental accessibility of the critical exponent µ of the YangLee edge singularities. They manifest themselves in divergences of the density functions g(θ), which quantify the distribution of the zeros of the partition function on the LeeYang unit circle in the complex plane. In accordance with the hypothesis of universality, a critical exponent close to the ...
YangLee Edge Singularities Determined From Experimental HighField Magnetization Data, Christian Binek, Wolfgang Kleemann, H. Aruga Katori
YangLee Edge Singularities Determined From Experimental HighField Magnetization Data, Christian Binek, Wolfgang Kleemann, H. Aruga Katori
Christian Binek Publications
The isothermal magnetization m (H) of the metamagnet FeCl_{2} is measured in axial magnetic fields 0 ≤ μ_{0}H_{a} ≤ 12 T at temperatures 34 ≤ T ≤ 53 K above the Néel temperature, where the system is essentially a twodimensional Ising ferromagnet. The analysis of the data indicates experimental accessibility of the critical exponent μ of the YangLee edge singularities. They manifest themselves in divergences of the density functions g(θ), which quantify the distribution of the zeros of the partition function on the LeeYang unit circle in the complex plane. In accordance with the hypothesis of universality, a critical ...
Magnetic States Of Granular Layered CofeAl_{2}O_{3}, J.B. Sousa, G.N. Kakazei, Y.G. Pogorelov, J.A.M. Santos, O. Petracic, Wolfgang Kleemann, Christian Binek, Susana Cardoso De Freitas, P.P. Freitas, M.M. Pereira De Azevedo, N.A. Lesnik, Stanislav Rokhlin, P.E. Wigen
Magnetic States Of Granular Layered CofeAl2O3, J.B. Sousa, G.N. Kakazei, Y.G. Pogorelov, J.A.M. Santos, O. Petracic, Wolfgang Kleemann, Christian Binek, Susana Cardoso De Freitas, P.P. Freitas, M.M. Pereira De Azevedo, N.A. Lesnik, Stanislav Rokhlin, P.E. Wigen
Christian Binek Publications
The granular layered magnetic system Co_{80}Fe_{20}(t)/Al_{2} O_{3} (3 nm), where the Co_{80}Fe_{20} layers of nominal thickness t form separate, almost spherical magnetic granules of typical diameter 23 nm between the Al_{2}O_{3} spacers, was studied. We discuss measurements of the dc and ac magnetic susceptibility χ for 1 nm
Magnetic Phase Diagram Of The Diluted Metamagnet Fe_{0.95}Mg_{0.05}Br_{2}, H. Aruga Katori, K. Katsumata, O. Petracic, Wolfgang Kleemann, T. Kato, Christian Binek
Magnetic Phase Diagram Of The Diluted Metamagnet Fe0.95Mg0.05Br2, H. Aruga Katori, K. Katsumata, O. Petracic, Wolfgang Kleemann, T. Kato, Christian Binek
Christian Binek Publications
The axial magnetic phase diagram of the antiferromagnet Fe_{0.95}Mg_{0.05}Br_{2} is studied by specific heat, superconducting quantum interference device, and Faraday rotation techniques. The diamagnetic impurities give rise to randomfield criticality along the secondorder phase line H_{c}(T) between T_{N}=13.1 K and a multicritical point at T_{m}≈5 K, and to a spinflop line between T_{m} and the critical endpoint temperature T_{e}≈3.5 K. The phase line H_{1}(T)c(T) ending at T_{m} is probably due to symmetric nondiagonal exchange.
Interacting Ferromagnetic Nanoparticles In Discontinuous Co_{80}Fe_{20}/Al_{2}O_{3} Multilayers: From Superspin Glass To Reentrant Superferromagnetism, W. Kleeman, O. Petracic, Christian Binek, G.N. Kakazei, Yu. G. Pogorelov, J.B. Sousa, Susana Cardoso De Freitas, P.P. Freitas
Interacting Ferromagnetic Nanoparticles In Discontinuous Co80Fe20/Al2O3 Multilayers: From Superspin Glass To Reentrant Superferromagnetism, W. Kleeman, O. Petracic, Christian Binek, G.N. Kakazei, Yu. G. Pogorelov, J.B. Sousa, Susana Cardoso De Freitas, P.P. Freitas
Christian Binek Publications
Dipolar superferromagnetism with reentrant lowtemperature superspin glass behavior is observed on a randomly distributed ferromagnetic nanoparticle systems in discontinuous metalinsulator multilayers [Co_{80}Fe_{20}/Al_{2}O_{3} (3 nm)] _{10} with nominal thickness 1.1<~t<~1.3 nm by use of ac susceptometry and dc magnetometry. At t=1.0 nm, superspin glasslike freezing is evidenced by the criticality of dynamic and nonlinear susceptibilities.