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Articles 1 - 30 of 38
Full-Text Articles in Physics
Magnetic Slime, Admin Stem For Success
Magnetic Slime, Admin Stem For Success
STEM for Success Showcase
Students learn chemistry and physics by making magnetic slime.
Spectroscopic Properties Of Ferroic Superlattices, Shiyu Fan
Spectroscopic Properties Of Ferroic Superlattices, Shiyu Fan
Doctoral Dissertations
The interplay between charge, structure, magnetism, and orbitals leads to rich physics and exotic cross-coupling in multifunctional materials. Superlattices provide a superb platform to study the complex interactions between different degrees of freedom. In this dissertation, I present a spectroscopic investigation of natural and engineered superlattices including FexTaS2 and (LuFeO3)m/(LuFe2O4)1 under external stimuli of temperature and magnetic field as well as chemical substitution. Studying the phase transitions, symmetry-breaking, and complex interface interactions from a microscopic viewpoint enhances fundamental understanding of coupling mechanism between different order parameters and the …
A Study Of The Frustrated Honeycomb Battery Material Na2ni2teo6, Nathan Christopher Episcopo
A Study Of The Frustrated Honeycomb Battery Material Na2ni2teo6, Nathan Christopher Episcopo
Open Access Theses & Dissertations
The P2-type layered hexagonal compound Na2Ni2TeO6 with Ni2+ on a honeycomb lattice was synthesized by the standard solid-state route. Structural characterization chemical phase purity was confirmed by Rietveld refinement of laboratory and synchrotron data. The crystal structure refines well in the P63/mcm space group. Single crystal growth trials using the self-flux-melt method were conducted with limited success. The magnetic transition temperature pertaining to Ni2+ lattice was confirmed by analysis of specific heat capacity to be . The magnetic susceptibility remains largely unchanged in magnetic field of and external pressure of . There is an almost linear response in isothermal magnetization …
The Magnetic Activity Of Low-Mass Stars, Tholang Mota
The Magnetic Activity Of Low-Mass Stars, Tholang Mota
DePaul Discoveries
The purpose of this research project is to study magnetically active low mass stars using data obtained with the Kepler space telescope. A sample of low mass stars was identified in the Kepler Objects of Interest (KOI) database by selecting stars with a temperature below 3,700 K. Data was obtained from the Mikulski Archive for Space Telescopes and analyzed using the MATLAB software. Light curves showing the stellar flux vs time were generated for approximately 20 stars, and features showing stellar flares, star spots and planetary transits were identified. We found a weak relationship between magnetic activity and stellar diameter.
Near Room Temperature Magnetocaloric Materials For Magnetic Refrigeration, Eduardo Martinez Teran
Near Room Temperature Magnetocaloric Materials For Magnetic Refrigeration, Eduardo Martinez Teran
Open Access Theses & Dissertations
Magnetic refrigeration (MR) is a cooling process based on the magnetocaloric effect (MCE) that is present to some extent in all magnetic materials, and the ones in which this effect is more appreciable are called magnetocaloric materials (MCM). The implementation of new designs and materials for the construction of cooling systems is a must do, being essential that these improved designs will reduce the environmental impact and increase the efficiency of their predecessors. In this thesis, the magnetocaloric effect theory is presented from a thermodynamic point of view and also the synthesis and study to a new Heusler alloy (MnFe2Ga) …
Oscillation Of The Ionosphere At Planetary-Wave Periods, Jeffrey M. Forbes, Astrid Maute, Xiaoli Zhang, Maura E. Hagan
Oscillation Of The Ionosphere At Planetary-Wave Periods, Jeffrey M. Forbes, Astrid Maute, Xiaoli Zhang, Maura E. Hagan
All Physics Faculty Publications
F‐region ionospheric oscillations at planetary‐wave (PW) periods (2–20 days) are investigated, with primary focus on those oscillations transmitted to the ionosphere by PW modulation of the vertically propagating tidal spectrum. Tidal effects are isolated by specifically designed numerical experiments performed with the National Center for Atmospheric Research thermosphere‐ionosphere‐electrodynamics general circulation model for October 2009, when familiar PW and tides are present in the model. Longitude versus day‐of‐month perturbations in topside F‐region electron density (Ne) of order ±30–50% at PW periods occur as a result of PW‐modulated tides. At a given height, these oscillations are mainly due to vertical oscillations in …
Rewriting Magnetic Phase Change Memory By Laser Heating, John Timmerwilke, Sy-Hwang Liou, Shu Fan Cheng, Alan S. Edelstein
Rewriting Magnetic Phase Change Memory By Laser Heating, John Timmerwilke, Sy-Hwang Liou, Shu Fan Cheng, Alan S. Edelstein
Sy-Hwang Liou Publications
Magnetic phase change memory (MAG PCM) consists of bits with different magnetic permeability values. The bits are read by measuring their effect on a magnetic probe field. Previously low permeability crystalline bits had been written in high permeability amorphous films of Metglas via laser heating. Here data is presented showing that by applying short laser pulses with the appropriate power to previously crystallized regions they can first be vitrified and then again crystallized. Thus, MAG PCM is rewriteable. Technical issues in processing the bits are discussed and results on thermal modeling are presented.
Structure Symmetry Determination And Magnetic Evolution In Sr2Ir1−XRhXO4, Feng Ye, Xiaoping Wang, Christina Hoffmann, Jinchen Wang, Songxue Chi, Masaaki Matsuda, Bryan C. Chakoumakos, Jaime A. Fernandez-Baca, Gang Cao
Structure Symmetry Determination And Magnetic Evolution In Sr2Ir1−XRhXO4, Feng Ye, Xiaoping Wang, Christina Hoffmann, Jinchen Wang, Songxue Chi, Masaaki Matsuda, Bryan C. Chakoumakos, Jaime A. Fernandez-Baca, Gang Cao
Physics and Astronomy Faculty Publications
We use single-crystal neutron diffraction to determine the crystal structure symmetry and the magnetic evolution in the rhodium-doped iridates Sr2Ir1−xRhxO4 (0≤ x ≤ 0.16). Throughout this doping range, the crystal structure retains a tetragonal symmetry (space group I41/a) with two distinct magnetic Ir sites in the unit cell forming staggered IrO6 rotation. Upon Rh doping, the magnetic order is suppressed and the magnetic moment of Ir4+ is reduced from 0.21μB/Ir for x=0 to 0.18μB/Ir for x=0.12. The magnetic structure …
Tunable Magnetic Properties Of Transition Metal Doped Mos2, Antonis N. Andiotis, Madhu Menon
Tunable Magnetic Properties Of Transition Metal Doped Mos2, Antonis N. Andiotis, Madhu Menon
Physics and Astronomy Faculty Publications
We report a detailed investigation of the electronic and magnetic properties of the transition metal (TM) doped two-dimensional (2D) MoS2 using ab initio calculations. The doping is achieved by substituting two or more Mo atoms by TM atoms of the 3d series. Additionally, the effect of codoping on the 2D MoS2 by cation-cation and cation-anion pairs is also investigated. Our results demonstrate that the TM doping of 2D MoS2 leads to a significant reduction of the energy gap and the appearance of magnetic features whose major characteristic is the ferromagnetic coupling of the TM dopants. The …
Magnetic Correlations And Pairing In The 1/5-Depleted Square Lattice Hubbard Model, Ehsan Khatami, Rajiv R.P. Singh, Warren E. Pickett, Richard T. Scalettar
Magnetic Correlations And Pairing In The 1/5-Depleted Square Lattice Hubbard Model, Ehsan Khatami, Rajiv R.P. Singh, Warren E. Pickett, Richard T. Scalettar
Faculty Publications
We study the single-orbital Hubbard model on the 1/5-depleted square-lattice geometry, which arises in such diverse systems as the spin-gap magnetic insulator CaV4O9 and ordered-vacancy iron selenides, presenting new issues regarding the origin of both magnetic ordering and superconductivity in these materials. We find a rich phase diagram that includes a plaquette singlet phase, a dimer singlet phase, a Néel and a block-spin antiferromagnetic phase, and stripe phases. Quantum Monte Carlo simulations show that the dominant pairing correlations at half filling change character from d wave in the plaquette phase to extended s wave upon transition to the Néel phase. …
Recent Ideas On The Calculation Of Lepton Anomalous Magnetic Moments, Michael I. Eides
Recent Ideas On The Calculation Of Lepton Anomalous Magnetic Moments, Michael I. Eides
Physics and Astronomy Faculty Publications
We discuss the recent claim [G. Mishima, arXiv:1311.7109; M. Fael and M. Passera, arXiv:1402.1575 [Phys. Rev. D (to be published)]] about discovery of a nonperturbative quantum-electrodynamic contribution of order (α/π)5 to lepton anomalous magnetic moments. We explain why this nonperturbative correction does not exist.
Isotropic Oscillator Under A Magnetic And Spatially Varying Electric Field, David L. Frost Mr., Frank Hagelberg
Isotropic Oscillator Under A Magnetic And Spatially Varying Electric Field, David L. Frost Mr., Frank Hagelberg
Undergraduate Honors Theses
We investigate the energy levels of a particle confined in the isotropic oscillator potential with a magnetic and spatially varying electric field. Here we are able to exactly solve the Schrodinger equation, using matrix methods, for the first excited states. To this end we find that the spatial gradient of the electric field acts as a magnetic field in certain circumstances. Here we present the changes in the energy levels as functions of the electric field, and other parameters.
The Jahn–Teller Effect And Electron–Phonon Interaction In La0.25ca0.75mn1−Xcrxo3, H. Zhou, G. Li, H. Chen, R. Zheng, Xiaojuan Fan, X. Li
The Jahn–Teller Effect And Electron–Phonon Interaction In La0.25ca0.75mn1−Xcrxo3, H. Zhou, G. Li, H. Chen, R. Zheng, Xiaojuan Fan, X. Li
Xiaojuan Fan
The ultrasonic (longitudinal and transverse) velocities and the transport and magnetic properties of polycrystalline La0.25Ca0.75Mn1-xCrxO3 (x = 0, 0.03, 0.05, and 0.07) have been studied systematically. It was found that with increasing Cr content, the resistivity increases, the charge-ordering transition temperature TCO shifts to low temperature, and the magnetic moment of the system is strengthened. From the temperature dependence of the ultrasonic velocities, one can establish that the Jahn-Teller energy and phonon exchange constant decrease with increasing Cr content.
Magnetic Correlations And Pairing In The 1/5-Depleted Square Lattice Hubbard Model, Ehsan Khatami, Rajiv R.P. Singh, Warren E. Pickett, Richard T. Scalettar
Magnetic Correlations And Pairing In The 1/5-Depleted Square Lattice Hubbard Model, Ehsan Khatami, Rajiv R.P. Singh, Warren E. Pickett, Richard T. Scalettar
Ehsan Khatami
We study the single-orbital Hubbard model on the 1/5-depleted square-lattice geometry, which arises in such diverse systems as the spin-gap magnetic insulator CaV4O9 and ordered-vacancy iron selenides, presenting new issues regarding the origin of both magnetic ordering and superconductivity in these materials. We find a rich phase diagram that includes a plaquette singlet phase, a dimer singlet phase, a Néel and a block-spin antiferromagnetic phase, and stripe phases. Quantum Monte Carlo simulations show that the dominant pairing correlations at half filling change character from d wave in the plaquette phase to extended s wave upon transition to the Néel phase. …
Diffusive Electron Heat Flow And Temperature Variance Along Magnetic Field Lines, Michael Kushlan
Diffusive Electron Heat Flow And Temperature Variance Along Magnetic Field Lines, Michael Kushlan
Physics Capstone Projects
In this research we examine how electron heat moves along magnetic field lines and how this affects temperature variations in plasmas. Specifically we wrote FORTRAN code to solve the electron temperature equation numerically. We also solved the steady state electron temperature equation analytically using an integrating factor. We verified that the numerical and analytical solutions obtained the same result. Finally we calculated the standard deviation of temperature in our domain for the steady state. Gaussian legendre quadrature was used to integrate various functions. We represented our magnetic field and heat source with Fourier series. The sin and cosine coefficients for …
Strong Magnetic Field Effect On Over-The-Barrier Transport In Pb-P-Hg 1-Xcdxte Schottky Barriers, V. V. Radantsev, V. V. Zavyalov
Strong Magnetic Field Effect On Over-The-Barrier Transport In Pb-P-Hg 1-Xcdxte Schottky Barriers, V. V. Radantsev, V. V. Zavyalov
All Physics Faculty Publications
It is usually believed that the over-the-barrier current in Schottky barriers (SB) on p-type semiconductor is controlled by heavy holes. However, there is an additional potential barrier caused by an oxide layer inevitably existing at the interface in real SB. For typical parameters of the barrier, its tunnelling transparency for light holes can be higher by three orders of magnitude than that for heavy holes. Thus, one can expect that the current is mainly due to the contribution of light holes. To clarify this problem, the investigation of carrier transport in a magnetic field is used as a key experiment …
Inductive Metal Identification, Paul Maggi
Inductive Metal Identification, Paul Maggi
Electrical Engineering
This project focuses on creating a device to differentiate between various types of metals via magnetic induction. Magnetic induction is used because it is both non-optical and non-contact. It achieves this by generating a varying magnetic field, which induces eddy currents in the metal. These eddy currents produce small disturbances in the surrounding magnetic field, which can be sensed with Hall Effect Sensors (HES). The primary challenge in this project was generating a sufficiently strong magnetic field to detectable disturbances. In order to achieve better results, a stronger magnetic field must be used as well as more sensitive Hall Effect …
Superspin Glass Behaviour Of Interacting Ferromagnetic Nanoparticles In Discontinuous Magnetic Multilayers, Christian Binek
Superspin Glass Behaviour Of Interacting Ferromagnetic Nanoparticles In Discontinuous Magnetic Multilayers, Christian Binek
Christian Binek
Discontinuous magnetic multilayers [Co80Fe20(t)/Al2O3(3nm)]10 with t = 0.9 and 1.0nm are studied by SQUID magnetometry and ac susceptibility. Owing to dipolar interaction the superparamagnetic cluster systems undergo collective glass-like freezing upon cooling. While both samples exhibit very similar glass temperatures Tg » 45 K and critical exponents zn » 10 and g » 1.4 as obtained from the temperature dependencies of the relaxation time, t, and the nonlinear susceptibility, c3, dynamical scaling reveals different critical exponents, b(0.9nm) »1.0 and b(1.0nm) » 0.6, respectively.
Light Diffraction By Field-Induced Non-Periodic Magnetic Domain Structures In Fecl2, Christian Binek
Light Diffraction By Field-Induced Non-Periodic Magnetic Domain Structures In Fecl2, Christian Binek
Christian Binek
The magnetic-field-induced mixed phase of the meta magnet FeCl2 gives rise to reduced transmittivity of circularly polarized light. Within the framework of the diffraction theory of thin random magnetic phase gratings and the assumption of field-dependent refractive indices of the antiferromagnetic domains the field dependence of the transmission is perfectly modeled.
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.
Random-Field Critical And Spin-Flop Behavior Of The Anisotropic Heisenberg Antiferromagnet Fe0.9mg0.1br2 In Axial Magnetic Fields, Christian Binek
Random-Field Critical And Spin-Flop Behavior Of The Anisotropic Heisenberg Antiferromagnet Fe0.9mg0.1br2 In Axial Magnetic Fields, Christian Binek
Christian Binek
Faraday optical measurements on the dilute hexagonal antiferromagnet Fe0.85Mg0.15Br2 in an external axial field reveal a spin-flop phase line ending at a multicritical point (Tm=8.1 K, Hm=1050 kA m-1) and crossover from random-exchange to random-field Ising criticality with an exponent Phi =1.40+or-0.04 in the vicinity of TN=11.1 K. Cusp-like behaviour of the specific heat at TN is discussed in view of recent Monte Carlo results.
Magnetic And Structural Properties Of Zinc-Doped Nickel Ferrite, Kanokporn Chattrakun
Magnetic And Structural Properties Of Zinc-Doped Nickel Ferrite, Kanokporn Chattrakun
Open Access Theses & Dissertations
We have used dc-magnetization, ac-magnetic susceptibility and x-ray diffraction (XRD) to investigate the microscopic origin of the magnetic property modifications induced by zinc doping in bulk and nano-sized nickel ferrite. Magnetic measurements indicate that the nanoparticle energy barrier to magnetization reversal, EB, and the bulk saturation magnetization, Ms, follow similar dependences on the zinc doping fraction, x. Both these magnetic quantities initially increase with increasing x, reach a maximum at x~0.5, and eventually decrease upon further doping. Synchrotron and laboratory powder XRD data show no evidence of significant structural modifications for x~0.5: we find the lattice …
Probing The Complex Magnetic, Electronic And Structural Properties In Correlated Manganese Oxides, Peng Gao
Probing The Complex Magnetic, Electronic And Structural Properties In Correlated Manganese Oxides, Peng Gao
Dissertations
Rare-earth Manganese Oxides (RMnO3) exhibit two distinct structural phases: the orthorhombic structure and the hexagonal structure. The doped orthorhombic phase exhibits a metal to insulator transition, charge ordering and a strong response of electron transport properties to magnetic fields (colossal magneto-resistance). At low temperatures, this system may also exhibit a finite polarization which couples to external magnetic fields. The hexagonal phase is known to have a large spontaneous polarization at high temperatures which couples to the low temperature magnetic order. These materials are important from the basic point of view of understanding strong electronic correlations and …
Resonant Microwave Cavity For 8.5-12 Ghz Optically Detected Electron Spin Resonance With Simultaneous Nuclear Magnetic Resonance, John S. Colton, L. R. Wienkes
Resonant Microwave Cavity For 8.5-12 Ghz Optically Detected Electron Spin Resonance With Simultaneous Nuclear Magnetic Resonance, John S. Colton, L. R. Wienkes
Faculty Publications
We present a newly developed microwave resonant cavity for use in optically detected magnetic resonance (ODMR) experiments. The cylindrical quasi-TE 011 mode cavity is designed to fit in a 1 in. magnet bore to allow the sample to be optically accessed and to have an adjustable resonant frequency between 8.5 and 12 GHz. The cavity uses cylinders of high dielectric material, so-called "dielectric resonators," in a double-stacked configuration to determine the resonant frequency. Wires in a pseudo-Helmholtz configuration are incorporated into the cavity to provide frequencies for simultaneous nuclear magnetic resonance (NMR). The system was tested by measuring cavity absorption …
Equatorial Ionospheric Electric Fields During The November 2004 Magnetic Storm, Bela G. Fejer, J. W. Jensen, T. Kikuchi, M. A. Abdu, J. L. Chau
Equatorial Ionospheric Electric Fields During The November 2004 Magnetic Storm, Bela G. Fejer, J. W. Jensen, T. Kikuchi, M. A. Abdu, J. L. Chau
Bela G. Fejer
[1] We use radar measurements from the Jicamarca Radio Observatory, magnetometer observations from the Pacific sector and ionosonde data from Brazil to study equatorial ionospheric electric fields during the November 2004 geomagnetic storm. Our data show very large eastward and westward daytime electrojet current perturbations with lifetimes of about an hour (indicative of undershielding and overshielding prompt penetration electric fields) in the Pacific equatorial region during the November 7 main phase of the storm, when the southward IMF, the solar wind and reconnection electric fields, and the polar cap potential drops had very large and nearly steady values. This result …
Evolution Of Equatorial Ionospheric Bubbles During A Large Auroral Electrojet Increase In The Recovery Phase Of A Magnetic Storm, M. J. Keskinen, S. L. Ossakow, Bela G. Fejer, J. Emmert
Evolution Of Equatorial Ionospheric Bubbles During A Large Auroral Electrojet Increase In The Recovery Phase Of A Magnetic Storm, M. J. Keskinen, S. L. Ossakow, Bela G. Fejer, J. Emmert
Bela G. Fejer
[1] We present a model and observations of the evolution of equatorial ionospheric bubbles during a large auroral electrojet (AE) index increase in the recovery phase of a geomagnetic storm. Using a three-dimensional time-dependent numerical simulation model, we find, for the 19–21 October 1998 storm, that the equatorial bubble evolution is different during storm time as compared to quiet time conditions. We have found that the storm time vertical drift in conjunction with reduced off-equatorial E region shorting is the primary mechanism that distinguishes the large AE increase recovery phase storm time evolution from the quiet time case. Comparison of …
Magnetospheric Electric Fields And Plasma Sheet Injections To Low-Lshells During The June 4-5, 1991 Magnetic Storm: Comparison Between The Rice Convectionmodel And Observations, T. W. Garner, R. A. Wolf, R. W. Spiro, W. J. Burke, Bela G. Fejer, S. Sazykin, J. L. Roeder, M. R. Hairston
Magnetospheric Electric Fields And Plasma Sheet Injections To Low-Lshells During The June 4-5, 1991 Magnetic Storm: Comparison Between The Rice Convectionmodel And Observations, T. W. Garner, R. A. Wolf, R. W. Spiro, W. J. Burke, Bela G. Fejer, S. Sazykin, J. L. Roeder, M. R. Hairston
Bela G. Fejer
[1] The major magnetic storm of 4–5 June 1991 was well observed with the Combined Release and Radiation Experiment (CRRES) satellite in the duskside inner magnetosphere and with three Defense Meteorological Satellite Program (DMSP) spacecraft in the polar ionosphere. These observations are compared to results from the Rice Convection Model (RCM), which calculates the inner magnetospheric electric field and particle distribution self-consistently. This case study, which uses the most complete RCM runs to date, demonstrates two significant features of magnetospheric storms, the development of subauroral polarization streams (SAPS) and plasma-sheet particle injection deep into the inner magnetosphere. In particular, the …
Magnetic And Transport Properties Of The V2– Vi3 Diluted Magnetic Semiconductor Sb2_Xmnxte3, Jeffrey Dyck, P. Svanda, P. Lostak, J. Horak, W. Chen, C. Uher
Magnetic And Transport Properties Of The V2– Vi3 Diluted Magnetic Semiconductor Sb2_Xmnxte3, Jeffrey Dyck, P. Svanda, P. Lostak, J. Horak, W. Chen, C. Uher
Jeffrey Dyck
We have measured electrical and magnetic properties of single crystals of Sb2_xMnxTe3 with x =0 – 0.045 at temperatures of 2 K to 300 K. Hall effect measurements indicate that each manganese atom donates approximately one hole to the valence band. The magnetic susceptibility is paramagnetic down to 2 K, and both Curie–Weiss and Brillouin analyses show that manganese substitutes for Sb and takes the Mn2+ state with S=5/2. Contrary to the case of III–V host matrices, manganese does not stimulate ferromagnetic order in the family of bulk layered V2– VI3 diluted magnetic semiconductors, at least in the range of …
Low Latitude Ionospheric Disturbance Electric Field Effects Duringthe Recovery Phase Of The October 19-21, 1998 Magnetic Storm, Bela G. Fejer, J. T. Emmert
Low Latitude Ionospheric Disturbance Electric Field Effects Duringthe Recovery Phase Of The October 19-21, 1998 Magnetic Storm, Bela G. Fejer, J. T. Emmert
Bela G. Fejer
[1] Low-latitude ionospheric electric fields and currents are often strongly disturbed during periods of enhanced geomagnetic activity. These perturbations can last for several hours after geomagnetic quieting. We use incoherent scatter radar measurements from Jicamarca and Arecibo during 19–21 October 1998 to study, for the first time, the low-latitude disturbance electric fields during the recovery phase of a large magnetic storm. On 19 October the Jicamarca data showed initially large and short-lived (time scale of about 10–20 min) upward and westward drift perturbations in the early afternoon sector, due to the penetration of strong magnetospheric electric fields probably driven by …
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.