Showing papers on "Magnetic semiconductor published in 2002"
01 Jan 2002
TL;DR: In this article, Ferromagnetic III-V Semiconductors and their Heterostructures and their spin-polarized transport from magnetic into non-magnetic Semiconductor Semiccondors are discussed.
Abstract: 1 Ferromagnetic III-V Semiconductors and Their Heterostructures.- 2 Spin Injection and Transport in Micro- and Nanoscale Devices.- 3 Electrical Spin Injection: Spin-Polarized Transport from Magnetic into Non-Magnetic Semiconductors.- 4 Spin Dynamics in Semiconductors.- 5 Optical Manipulation, Transport and Storage of Spin Coherence in Semiconductors.- 6 Spin Condensates in Semiconductor Microcavities.- 7 Spins for Quantum Information Processing.- 8 Electron Spins in Quantum Dots as Qubits for Quantum Information Processing.- 9 Regulated Single Photons and Entangled Photons From a Quantum Dot Microcavity.
1,356 citations
TL;DR: In this paper, materials design of new functional diluted magnetic semiconductors (DMSs) is presented based on first principles calculations, and the stability of the ferromagnetic state in ZnO-, ZnS-, Zns, ZnSe and ZnTe-based DMSs is investigated systematically.
Abstract: Materials design of new functional diluted magnetic semiconductors (DMSs) is presented based on first principles calculations. The stability of the ferromagnetic state in ZnO-, ZnS-, ZnSe-, ZnTe-, GaAs- and GaN-based DMSs is investigated systematically and it is suggested that V- or Cr-doped ZnO, ZnS, ZnSe and ZnTe are candidates for high-TC ferromagnetic DMSs. V-, Cr- or Mn-doped GaAs and GaN are also candidates for high-TC ferromagnets. It is also shown that Fe-, Co- or Ni-doped ZnO is ferromagnetic. In particular, the carrier-induced ferromagnetism in ZnO-based DMSs is investigated and it is found that their magnetic states are controllable by changing the carrier density. The origin of the ferromagnetism in the DMSs is also discussed.
771 citations
16 Jan 2002
TL;DR: The current status and prospects of research on ferromagnetism in semiconductors are reviewed in this article, where the authors present a quantitative comparison between experimental and theoretical results for Mn-based III-V and II-VI compounds, showing that the current theory of the exchange interactions mediated by holes in the valence band describes correctly the values of Curie temperatures.
Abstract: The current status and prospects of research on ferromagnetism in semiconductors are reviewed The question of the origin of ferromagnetism in europium chalcogenides, chromium spinels and, particularly, in diluted magnetic semiconductors is addressed The nature of electronic states derived from 3d of magnetic impurities is discussed in some details Results of a quantitative comparison between experimental and theoretical results, notably for Mn-based III-V and II-VI compounds, are presented This comparison demonstrates that the current theory of the exchange interactions mediated by holes in the valence band describes correctly the values of Curie temperatures T_C magnetic anisotropy, domain structure, and magnetic circular dichroism On this basis, chemical trends are examined and show to lead to the prediction of semiconductor systems with T_C that may exceed room temperature, an expectation that are being confirmed by recent findings Results for materials containing magnetic ions other than Mn are also presented emphasizing that the double exchange involving hoping through d states may operate in those systems
663 citations
TL;DR: In this article, the lattice constant of c axis of wurtzite Zn1−xCoxO follows Vergard's law for 0
Abstract: We report on the high-temperature ferromagnetism in Co-doped ZnO films fabricated by the sol–gel method above 350 K. The lattice constant of c axis of wurtzite Zn1−xCoxO follows Vergard’s law for 0
644 citations
TL;DR: Analytical expressions for the Curie temperature and the magnetization in the limit of low carrier density are derived, obtaining excellent quantitative agreement with Monte Carlo simulation results and good qualitative agreement with experimental results.
Abstract: We theoretically study the development of spontaneous magnetization in diluted magnetic semiconductors as arising from a percolation of bound magnetic polarons. Within the framework of a generalized percolation theory we derive analytic expressions for the Curie temperature and the magnetization in the limit of low carrier density, obtaining excellent quantitative agreement with Monte Carlo simulation results and good qualitative agreement with experimental results.
634 citations
TL;DR: In this paper, the properties of Zn1−xMnxO (x=0.1 and 0.3) thin films grown on Al2O3(00⋅1) substrates using laser molecular-beam epitaxy were investigated.
Abstract: We report on ferromagnetic characteristics of Zn1−xMnxO (x=0.1 and 0.3) thin films grown on Al2O3(00⋅1) substrates using laser molecular-beam epitaxy. By increasing the Mn content, the films exhibited increases in both the c-axis lattice constant and fundamental band gap energy. The Curie temperature obtained from temperature-dependent magnetization curves was 45 K for the film with x=0.3, depending on the Mn composition in the films. The remanent magnetization and coercive field of Zn0.9Mn0.1O at 5 K were 0.9 emu/g and 300 Oe, respectively. For Zn0.7Mn0.3O, the remanent magnetization at 5 K increased to 3.4 emu/g.
518 citations
TL;DR: In this article, the authors review recent progress made in the field of semiconductor spintronics, a branch of the semiconductor electronics where both charge and spin degrees of freedom play an important role in realizing unique functionalities.
Abstract: We review recent progress made in the field of semiconductor spintronics, a branch of semiconductor electronics where both charge and spin degrees of freedom play an important role in realizing unique functionalities. We first describe the new spin-dependent phenomena found in semiconductors including carrier-induced ferromagnetism in III-V compounds, followed by an account of our current understanding of such spin-dependent phenomena. Then we summarize the challenges the semiconductor spintronics has to meet in order for it to be a success as "electronics".
494 citations
TL;DR: In this paper, a strong correlation between the location of Mn sites in ferromagnetic Ga{sub 1-x}Mn{sub x}As measured by channeling Rutherford backscattering and by particle induced x-ray emission experiments and its Curie temperature was reported.
Abstract: We report a strong correlation between the location of Mn sites in ferromagnetic Ga{sub 1-x}Mn{sub x}As measured by channeling Rutherford backscattering and by particle induced x-ray emission experiments and its Curie temperature. The concentrations of free holes determined by electrochemical capacitance-voltage profiling and of uncompensated Mn{sup ++} spins determined from SQUID magnetization measurements are found to depend on the concentration of unstable defects involving highly mobile Mn interstitials. This leads to large variations in T{sub c} of Ga{sub 1-x}Mn{sub x}As when it is annealed at different temperatures in a narrow temperature range. The fact that annealing under various conditions has failed to produce Curie temperatures above {approx}110K is attributed to the existence of an upper limit on the free hole concentration in low-temperature-grown Ga{sub 1-x}Mn{sub x}As.
471 citations
TL;DR: Wurtzite (Ga,Mn)N films showing ferromagnetic behaviour at room temperature were successfully grown on sapphire(0, 0, 0 1) substrates by molecular beam epitaxy using ammonia as a nitrogen source as mentioned in this paper.
371 citations
TL;DR: Proper choice of molecular precursors and kinetically driven low-temperature growth afford dopant controlled 1-D Cd1-xMn(x)S nanorods at high levels of Mn, which is supported by repeated surface exchange experiments and X-ray diffraction and electron paramagnetic resonance (EPR) analyses.
Abstract: Shape- and dopant-controlled magnetic semiconductor nanocrystals have been achieved by the thermolysis of nonpyrophoric and less reactive single molecular precursors under a monosurfactant system. Reaction parameters governing both the intrinsic crystalline phase and the growth regime (kinetic vs thermodynamic) are found to be important for the synthesis of various shapes of MnS nanocrystals that include cubes, spheres, 1-dimensional (1-D) monowires, and branched wires (bipods, tripods, and tetrapods). Obtained nanowires exhibit enhanced optical and magnetic properties compared to those of 0-D nanospheres. Proper choice of molecular precursors and kinetically driven low-temperature growth afford dopant controlled 1-D Cd1-xMn(x)S nanorods at high levels (up to approximately 12%) of Mn, which is supported by repeated surface exchange experiments and X-ray diffraction (XRD) and electron paramagnetic resonance (EPR) analyses.
370 citations
TL;DR: In this article, the authors characterized Zn1−xCoxO (x=0.25) films grown on sapphire (0001) substrates by pulsed laser deposition using various growth conditions to investigate the growth condition dependence of properties of Co-doped ZnO films.
Abstract: We have characterized Zn1−xCoxO (x=0.25) films grown on sapphire (0001) substrates by pulsed laser deposition using various growth conditions to investigate the growth condition dependence of properties of Co-doped ZnO films. The substrate temperature (TS) was varied from 300 to 700 °C and the O2 pressure (PO2) from 10−6 to 10−1 Torr. When TS is relatively low (≲600 °C), homogeneous alloy films with a wurtzite ZnO structure are grown and predominantly paramagnetic, whereas inhomogeneous films of wurtzite ZnO phase mixed with rock-salt CoO and hexagonal Co phases form when TS is relatively high and PO2 is fairly low (≲10−5 Torr). The presence of Co clusters leads to room temperature ferromagnetism in inhomogeneous films. The temperature dependence of the magnetization for the homogeneous Zn1−xCoxO (x=0.25) films shows spin-glass behavior at low temperature and high temperature Curie–Weiss behavior with a large negative value of the Curie–Weiss temperature, indicating strong antiferromagnetic exchange coupl...
TL;DR: In this paper, a GaMnN thin film was synthesized using gas-source molecular-beam epitaxy and magnetic characterization performed using a squid magnetometer showed evidence of ferromagnetic ordering at room temperature for all samples.
Abstract: GaMnN thin films were synthesized using gas-source molecular-beam epitaxy. Mn concentrations between 3 and 12 at. % were investigated. No evidence of second-phase formation was observed by powder x-ray diffraction or high-resolution cross section transmission electron microscopy in films with 9% or less Mn. The films were n type as determined by capacitance–voltage or Hall analysis. Magnetic characterization performed using a squid magnetometer showed evidence of ferromagnetic ordering at room temperature for all samples. In agreement with theoretical predictions, material with 3% Mn showed the highest degree of ordering per Mn atom. At 320 K, the samples show a nonzero magnetization indicating a TC above room temperature.
TL;DR: In this article, annealing Ga1−xMnxAs thin films at temperatures significantly lower than in previous studies, and monitoring the resistivity during growth, an unprecedented high Curie temperature and conductivity can be obtained.
Abstract: We show that by annealing Ga1−xMnxAs thin films at temperatures significantly lower than in previous studies, and monitoring the resistivity during growth, an unprecedented high Curie temperature TC and conductivity can be obtained. TC is unambiguously determined to be 118 K for Mn concentration x=0.05, 140 K for x=0.06, and 120 K for x=0.08. We also identify a clear correlation between TC and the room temperature conductivity. The results indicate that Curie temperatures significantly in excess of the current values are achievable with improvements in growth and post-growth annealing conditions.
TL;DR: In this paper, the synthesis of room-temperature ferromagnetic semiconductors, Zn1−xFexO, was reported, and the essential ingredient in achieving room temperature ferromagnetism in bulk Zn0.94Fe0.05Cu0.01O was found to be additional Cu doping.
Abstract: Successful synthesis of room-temperature ferromagnetic semiconductors, Zn1−xFexO, is reported. The essential ingredient in achieving room-temperature ferromagnetism in bulk Zn1−xFexO was found to be additional Cu doping. A transition temperature as high as 550 K was obtained in Zn0.94Fe0.05Cu0.01O; the saturation magnetization at room temperature reached a value of 0.75μB per Fe. A large magnetoresistance was also observed below 100 K.
TL;DR: In this paper, the authors developed a model in which polarons interact via both the standard direct carrier-carrier exchange interaction (due to virtual carrier hopping) and an indirect carrier-ion carrier exchange interaction, and the optimal values of the model parameters were determined as a function of temperature.
Abstract: The magnetic behavior of insulating doped diluted magnetic semiconductors (DMS's) is characterized by the interaction of large collective spins known as bound magnetic polarons. Experimental measurements of the susceptibility of these materials have suggested that the polaron-polaron interaction is ferromagnetic, in contrast to the antiferromagnetic carrier-carrier interactions that are characteristic of nonmagnetic semiconductors. To explain this behavior, a model has been developed in which polarons interact via both the standard direct carrier-carrier exchange interaction (due to virtual carrier hopping) and an indirect carrier-ion-carrier exchange interaction (due to the interactions of polarons with magnetic ions in an interstitial region). Using a variational procedure, the optimal values of the model parameters were determined as a function of temperature. At temperatures of interest, the parameters describing polaron-polaron interactions were found to be nearly temperature-independent. For reasonable values of these constant parameters, we find that indirect ferromagnetic interactions can dominate the direct antiferromagnetic interactions and cause the polarons to align. This result supports the experimental evidence for ferromagnetism in insulating doped DMS's.
TL;DR: In this paper, the effects of rapid thermal annealing under vacuum on the CoFe-doped ZnO [Zn 1−x(Co 0.5Fe0.5)xO] films grown by reactive magnetron co-sputtering were investigated.
Abstract: We have investigated the effects of rapid thermal annealing under vacuum on the CoFe-doped ZnO [Zn1−x(Co0.5Fe0.5)xO] films grown by reactive magnetron co-sputtering. At least up to x=0.15, the films have the single phase of the same wurtzite structure as pure ZnO. Ferromagnetism was observed for the CoFe-doped ZnO films. We found that rapid thermal annealing leads to a remarkable increase in the spontaneous magnetization of the CoFe-doped ZnO as well as the electron concentration. The annealing also leads to a significant increase in the Curie temperature (TC), resulting in room temperature ferromagnetism with TC>300 K for the CoFe-doped ZnO films.
TL;DR: A theory of spin-polarized transport in inhomogeneous magnetic semiconductors is developed and applied to magnetic/nonmagnetic p-n junctions, and it is demonstrated that only nonequilibrium spin can be injected across the space-charge region of a p- n junction.
Abstract: A theory of spin-polarized transport in inhomogeneous magnetic semiconductors is developed and applied to magnetic/nonmagnetic p-n junctions. Several phenomena with possible spintronic applications are predicted, including spin-voltaic effect, spin valve effect, exponential and giant magnetoresistance. It is demonstrated that only nonequilibrium spin can be injected across the space-charge region of a p-n junction, so that there is no spin injection (or extraction) at low bias.
TL;DR: In this article, structural, optical and magnetic properties of high quality epitaxial Zn 1− x Mn x O (diluted magnetic semiconductor) films were investigated using a pulsed laser deposition technique.
TL;DR: The presence of ferromagnetic clusters and hysteresis to temperatures of at least 330 K is attributed to disorder and proximity to a metal-insulating transition.
Abstract: Ion implantation of Mn ions into hole-doped GaP has been used to induce ferromagnetic behavior above room temperature for optimized Mn concentrations near 3 at. %. The magnetism is suppressed when the Mn dose is increasedor decreased away from the 3 at. % value, or when n-type GaP substrates are used. At low temperatures the saturated moment is on the order of 1 Bohr magneton, and the spin wave stiffness inferred from the Bloch-law T 3 / 2 dependence of the magnetization provides an estimate T c = 385 K of the Curie temperature that exceeds the experimental value, T c = 270 K. The presence of ferromagnetic clusters and hysteresis to temperatures of at least 330 K is attributed to disorder and proximity to a metal-insulating transition.
TL;DR: In this paper, the authors investigated Co-doped TiO2 thin films grown by reactive co-sputtering and found a single phase polycrystalline rutile structure, without any segregation of Co into particulates within the instrumental resolution limit.
Abstract: We have investigated Co-doped TiO2 thin films grown by reactive co-sputtering. X-ray diffraction showed a single phase polycrystalline rutile structure, without any segregation of Co into particulates within the instrumental resolution limit. The atomic content of Co ranged from 1% to 12%. The temperature dependence of resistivity showed an extrinsic semiconducting behavior. From optical absorption measurements, the band gap Eg≈3.25±0.05 eV was found, independent of the Co concentration, and in agreement with a literature value. Room temperature M-H loops showed a ferromagnetic behavior for Co content higher than 3%. The magnetic moment per Co atom was estimated to be about 0.94 μB, suggesting a low spin configuration of Co ions. The temperature dependence of remanent magnetization revealed a Curie temperature higher than 400 K for Co content of 12%.
TL;DR: In this paper, the authors derived a drift-diffusion equation for spin polarization in semiconductors by consistently taking into account electric-field effects and nondegenerate electron statistics and identified a high-field diffusive regime which has no analog in metals.
Abstract: In semiconductor spintronic devices, the semiconductor is usually lightly doped and nondegenerate, and moderate electric fields can dominate the carrier motion. We recently derived a drift-diffusion equation for spin polarization in semiconductors by consistently taking into account electric-field effects and nondegenerate electron statistics and identified a high-field diffusive regime which has no analog in metals. Here spin injection from a ferromagnet (FM) into a nonmagnetic semiconductor (NS) is extensively studied by applying this spin drift-diffusion equation to several typical injection structures such as FM/NS, FM/NS/FM, and FM/NS/NS structures. We find that in the high-field regime spin injection from a ferromagnet into a semiconductor is enhanced by several orders of magnitude. For injection structures with interfacial barriers, the electric field further enhances spin injection considerably. In FM/NS/FM structures high electric fields destroy the symmetry between the two magnets at low fields, where both magnets are equally important for spin injection, and spin injection becomes determined by the magnet from which carriers flow into the semiconductor. The field-induced spin injection enhancement should also be insensitive to the presence of a highly doped nonmagnetic semiconductor $({\mathrm{NS}}^{+})$ at the FM interface, thus ${\mathrm{F}\mathrm{M}/\mathrm{N}\mathrm{S}}^{+}/\mathrm{NS}$ structures should also manifest efficient spin injection at high fields. Furthermore, high fields substantially reduce the magnetoresistance observable in a recent experiment on spin injection from magnetic semiconductors.
TL;DR: In this article, an oxide-diluted magnetic semiconductor with rutile structure, Mn-doped SnO2, has been fabricated by pulsed-laser deposition.
Abstract: Epitaxial films of an oxide-diluted magnetic semiconductor with rutile structure, Mn-doped SnO2, have been fabricated by pulsed-laser deposition. As the Mn content increases, systematic changes in lattice constants and in-gap absorption are observed. Magnetization measurements show almost paramagnetic behavior. The injection of n-type carrier over 1020 cm−3 is achieved by Sb doping. A Sn0.95Mn0.05O2:Sb film shows giant positive magnetoresistance as large as 60% at 5 K.
TL;DR: The synthesis of colloidal oxide DMS-QDs introduces a new category of magnetic semiconductor materials available for detailed physical study and application in nanotechnology.
Abstract: Methods for introducing new magnetic, optical, electronic, photophysical, or photochemical properties to semiconductor nanocrystals are attracting intense applications-oriented interest. In this communication, we report the preparation and electronic absorption spectroscopy of colloidal ZnO DMS-QDs. Our synthetic procedure involves modification of literature methods known to yield highly crystalline and relatively monodisperse nanocrystals of pure ZnO to allow introduction of transition-metal dopants. We use ligand-field electronic absorption spectroscopy as a dopant-specific optical probe to monitor dopant incorporation during nanocrystal growth and to verify internal substitutional doping in Co2+:ZnO and Ni2+:ZnO DMS-QDs. To the best of our knowledge, these are the first free-standing oxide DMS-QDs reported. The synthesis of colloidal oxide DMS-QDs introduces a new category of magnetic semiconductor materials available for detailed physical study and application in nanotechnology.
TL;DR: The position of the Mn3+/2+ acceptor level at 1.8 eV above the valence-band edge of GaN makes the realization of carrier-mediated ferromagnetism rather unlikely in GaN:Mn as discussed by the authors.
Abstract: Molecular-beam-epitaxy grown GaN:Mn and AlN:Mn layers with Mn concentrations around 1020 cm−3 were investigated by optical absorption and photoconductivity measurements. From electron spin resonance Mn is known to be mostly present in the neutral acceptor state in GaN without codoping. This leads to a reassignment of the optical absorption features to a charge transfer from the neutral Mn3+ oxidation state, either by direct photoionization at 1.8 eV or through a photothermal ionization process via an excited state at 1.42 eV above the Mn3+ ground state by spin-allowed Mn3+ 5E→5T internal absorption. The position of the Mn3+/2+ acceptor level at 1.8 eV above the valence-band edge of GaN makes the realization of carrier-mediated ferromagnetism rather unlikely in GaN:Mn.
TL;DR: In this paper, a new III-V nitride-based diluted magnetic semiconductor GaCrN has been successfully synthesized for the first time, which showed a ferromagnetic behavior with the Curie temperature of higher than 400 K and clear saturation and hysteresis were observed in the magnetization versus magnetic field curves at all measuring temperatures (10-400 K).
TL;DR: Correlation of SQUID results, pXRD, and Raman measurements suggests that the observed enhancement of magnetic superexchange between Co(2+) dopant ions in this confined system arises from changes in the nature of coupling in size-restricted materials.
Abstract: In this study, we report structural, vibrational, and magnetic data providing evidence of random ion displacement in the core of CdSe quantum dots on the Cd2+ sites by Co2+ ions (between x = 0 and 0.30). Structural evidence for core doping is obtained by analyzing the powder X-ray diffraction (pXRD), data which exhibits a linear lattice compression with increasing Co2+ concentration, in accord with Vegard's law. Correlated with the pXRD shift, a hardening of the CdSe longitudinal optical phonon mode and a new local vibrational mode are observed which track Co2+ doping concentration. Consistent with the observed core doping, superconducting quantum interference device (SQUID) measurements indicate a surprising increase for the onset of spin glass behavior by an order of magnitude over bulk Co:CdSe. Correlation of SQUID results, pXRD, and Raman measurements suggests that the observed enhancement of magnetic superexchange between Co2+ dopant ions in this confined system arises from changes in the nature of c...
TL;DR: In this paper, the magnetism and the electronic structure of II-VI compound-based diluted magnetic semiconductors (DMSs) are investigated based on ab initio calculations.
Abstract: The magnetism and the electronic structure of II-VI compound-based diluted magnetic semiconductors (DMSs) are investigated based on ab initio calculations. The stability of the ferromagnetic state in ZnO-, ZnS-, ZnSe- and ZnTe-based DMSs is investigated systematically and materials design for ferromagnetic DMSs is given. In all host materials, it is found that V- and Cr-doped systems are ferromagnetic and Mn-doped systems are spin-glass state. On the other hand, for Fe-, Co- and Ni-doped systems, the ferromagnetic state is stable in ZnO-based DMS, however, the spin-glasss state is stable in ZnS-, ZnSe- and ZnTe-based DMSs. The carrier-induced ferromagnetism in ZnO-based DMSs is also investigated and it is found that their magnetic states are controllable by changing the carrier density. Analysing the calculated density of states, the mechanism to stabilize the ferromagnetic state in the DMSs is discussed.
TL;DR: In this article, a drift-diffusion equation for spin polarization in semiconductors was derived by consistently taking into account electric-field effects and non-degenerate electron statistics.
Abstract: We derive a drift-diffusion equation for spin polarization in semiconductors by consistently taking into account electric-field effects and nondegenerate electron statistics. We identify a high electric-field diffusive regime which has no analog in metals. In this regime there are two distinct spin-diffusion lengths. Furthermore, spin injection from a ferromagnetic metal into a semiconductor is enhanced by several orders of magnitude. This enhancement also occurs for high electric-field spin injection through a spin-selective interfacial barrier.
TL;DR: In this article, a room-temperature ferromagnetic transition was detected in Cr-doped GaN single crystals with a Tc=280 K. The coercive field by magnetization-magnetic field hysteresis curve at 250 K was 54 Oe.
Abstract: We report on the discovery of a room-temperature ferromagnetism in Cr-doped GaN single crystals with a Tc=280 K. The addition of Cr into GaN single crystals grown by the flux method induces the lattice constant increase due to the larger Cr atomic radius. In x-ray photoelectron spectroscopy measurement, Cr 2p3/2 core-level exhibited spectra near 575.7 eV. This binding energy is similar to the reported value of CrN. The coercive field by magnetization–magnetic field (M–H) hysteresis curve at 250 K was 54 Oe. We verified the presence of ferromagnetic transition in the temperature dependence of the electrical resistance measurements. We discuss the ferromagnetic ordering in Cr-doped GaN bulk single crystals excluding the contribution of the substrate crystal structure.
TL;DR: In this paper, the temperature dependencies of electrical resistance and carrier concentration were measured to investigate the relation between the ferromagnetism and transport property, showing coexistence of ferromagnetic and paramagnetic phases.
Abstract: Mn-doped GaN films on sapphire (0001) substrates were grown by molecular beam epitaxy system using ammonia as nitrogen source. The result of magnetization measurement gives Curie temperature as high as 940 K. The field and temperature dependencies of the magnetization show coexistence of ferromagnetic and paramagnetic phases. In addition, the temperature dependencies of electrical resistance and carrier concentration were measured to investigate the relation between the ferromagnetism and transport property. Below about 10 K, a similar anomalous increase of magnetization and resistance is observed.