Mixed Magnetic Phase Research Articles

Paramagnetism found in Mn-doped CuO nanofibers at room temperature explained by XPS , XAS and Rietveld method

CuO and 3 % Mn-doped CuO nanofibers were synthesized employing the electrospinning method. X-ray diffraction (XRD) verified a monoclinic phase with a C 2/c space group. An electronic density analysis, obtained using Fullprof software, was projected on the (110) and (001) planes for both materials, showing modifications in the Cu positions. This fact generated vacancies involved in the paramagnetism formation in the Mn-doped CuO nanofibers, in contrast to the mixed magnetic phase composed by both ferromagnetic and paramagnetic behaviors found in the undoped CuO. The vacancy amount was quantified by X-ray absorption spectroscopy (XAS) applying CASTEP software. In addition, an analysis from Cu 2p XPS peaks supports the predicted Cu-Cu rearrangement by the Fullprof software study, while the presence of Cu1+ confirms the substitution of Mn for Cu in the doped sample.

B-site disorder driven Griffiths-like phase and electrochemical behavior in Y2NiCrO6 double perovskite

In this investigation, nanoparticles of B-site disordered Y2NiCrO6 (YNCO) double perovskite were synthesized by the facile sol–gel method to evaluate their magnetic and electrochemical properties. Their crystallographic structure is monoclinic and the average size of the particles is 79±16 nm. XPS analysis indicated a mixed oxidation states of B-site transition metals Ni2+/Ni3+ and Cr2+/Cr3+. The mixed valence states of Ni and Cr, along with the mixed magnetic phases of YNCO, constitute a signature of the B-site disorder. This antisite disorder contributed to the observation of a Griffiths-like phase arising from ferromagnetic short-range interactions above the magnetic transition up to the Griffiths temperature, T G = 137 K. The synthesized YNCO double perovskite demonstrated a promising behavior as an electrode material for electrochemical supercapacitors. In a three-electrode system, it displayed a specific capacitance of 270 F g−1 at a current density of 0.5 A g−1. In a symmetric two-electrode system, YNCO exhibited a specific capacitance of 180 F g−1 at 0.5 A g−1, alongside an energy density of 6.25 Wh kg−1 at 250 W kg−1 power density. In both cases, we employed a mild 0.5 M neutral aqueous Na2SO4 solution as the electrolyte, in contrast to the typically employed corrosive and concentrated alkaline aqueous solution. The fascinating magnetic and charge storage properties of the B-site disordered YNCO double perovskite indicate its potential for use in spintronic devices and as efficient electrodes in symmetric hybrid supercapacitors.

Influence of Ni substitution on the magnetic properties of PrCoO3: A comprehensive study

The influence of nickel (Ni) ions on the structural and magnetic properties of PrCo1-xNixO3 perovskites was investigated. The samples were prepared using a sol-gel chemical auto-combustion route. The Rietveld refined X-ray diffraction patterns show that all samples were single-phase polycrystalline with orthorhombic (Pbnm) perovskite symmetry. Fourier transform infrared spectroscopy (FTIR) showed that with increasing Ni dopant content, the spin state changed from a low to an intermediate spin state (LS→IS), leading to an increase in the Co3+ population in the IS state, which improved the stability of the IS state. X-ray photoelectron spectroscopy confirmed the presence of mixed valence states (Co3+/Co4+) and oxygen vacancies. Ni-substituted PrCoO3 compounds exhibited mixed magnetic phases, which were separated by a theoretical model. The susceptibility curves were fitted with the Curie–Weiss law, and the negative value of the Curie–Weiss temperature indicated a strong predominance of antiferromagnetic (AFM) interactions over ferromagnetic (FM) ordering. However, when the Ni content in the host lattice increased, the FM coupling via double exchange became stronger. Thus, saturated FM ordering was achieved with an optimum doping level of Ni ions.

Superparamagnetic characteristic of surface capped Mg0.5Zn0.5Fe2O4 nanoparticles reinforced polycarbonate nanocomposite fibers with mixed magnetic phases

The purpose of this work is to prepare magnetic polycarbonate nanocomposite fibers from nonmagnetic polycarbonate material by electrospinning method. This was achieved by the incorporation of oleic acid capped magnesium zinc ferrite (Mg0.5Zn0.5Fe2O4) nanoparticles during the spinning process. The presence of uniformly distributed surface capped Mg0.5Zn0.5Fe2O4 nanoparticles in the polymer nanofibers was detected by TEM investigation. The nanocomposite fibers retained and exhibited the excellent surface morphology as that of the plane polycarbonate fibers prepared under the same solution and spinning parameters. FT-IR and XRD studies revealed that, there did not happen any degradation to the polycarbonate material even with a high nanofiller load or under a high applied potential during electrospinning. UV-Visible spectral study shows that the polycarbonate nanocomposite fibers attained attractive visible light absorption power. The increased polymer entanglement by the proper interaction with the ferrite nanoparticles attributes to the increase in the glass transition temperature of the nanocomposite fibers. The VSM analysis was carried out to find the magnetic parameters like saturation magnetization, coercivity and retentivity of the composite fibers. Mossbauer spectral analysis was done to know the isomer shift, quadrupole splitting and the average hyperfine field. PC-Mg0.5Zn0.5Fe2O4 composite nanofibers exhibit quadrupole splitting values between 0.35 and 0.57 mm/s

Structural analysis and magnetic properties of cobalt-doped nanotitania

The study is an attempt to bridge the gap between experimental observations and the theoretical predictions on cobalt (Co) doped TiO2 nanoparticles prepared by low cost sol-gel method. Single phase anatase TiO2 nanocrystals with particle size ranging between 16 and 32 nm observed minor distortions in TiO2 unit cell, after cobalt substitution (3 and 5 at.%), due to its larger ionic radius, which leads to creation of oxygen vacancies. Doped TiO2 showed significant diminution from 3.51 to 3.25 eV in the band gap, supported by density functional theory. Presence of nonlinear magnetization within lower field region was also observed which indicate the existence of weak ferromagnetism dominated by paramagnetic behaviour at high field region, suggesting a mixed magnetic phase. Magnetic observations are well supported with bound magnetic polaron (BMP) model. The observed band gap shrinkage and magnetic behaviour both are associated to the oxygen vacancies created by Co doping.

Effect of Mo doping on the electrical and magnetic properties of antiferromagnetic CrSe

Recently 2-dimentional (2D) magnetic materials have gained a lot of attention due to their peculiar magnetic properties, originated from the quantum confinement. Here, we report on the synthesis, magnetic and electrical transport properties of Mo doped Cr1-xMoxSe (x = 0.0, 0.01, and 0.03) polycrystalline systems. Room temperature powder X-ray diffraction (XRD) data confirm that all the samples are formed into the hexagonal crystal structure with a space group of P63/mmc. Electrical resistivity measurements suggest that all the samples are metallic in nature. From magnetic measurements, we observe a bifurcation between ZFC and FC curves in all the samples almost at the same temperature of 225 K, suggesting for an antiferromagnetic transition at this temperature that is not affected with Mo doping. Magnetization measurements suggest for a mixed magnetic phase at low temperatures, means, weak ferromagnetism is found in addition to the antiferromagnetic ordering for the parent system. Mo doping leads to a couple of additional antiferromagnetic magnetic transitions. We further noticed decreasing magnetic moment with increasing Mo doping.

Magnetism in metastable and annealed compositionally complex alloys

Compositionally complex materials (CCMs) present a potential paradigm shift in the design of magnetic materials. These alloys exhibit long-range structural order coupled with limited or no chemical order. As a result, extreme local environments exist with a large variations in the magnetic energy terms, which can manifest large changes in the magnetic behavior. In the current work, the magnetic properties of (Cr, Mn, Fe, Ni) alloys are presented. These materials were prepared by room-temperature combinatorial sputtering, resulting in a range of compositions with a single bcc structural phase and no chemical ordering. The combinatorial growth technique allows CCMs to be prepared outside of their thermodynamically stable phase, enabling the exploration of otherwise inaccessible order. The mixed ferromagnetic and antiferromagnetic interactions in these alloys causes frustrated magnetic behavior, which results in an extremely low coercivity $(<1\phantom{\rule{0.16em}{0ex}}\mathrm{mT})$, which increases rapidly at 50 K. At low temperatures, the coercivity achieves values of nearly 500 mT, which is comparable to some high-anisotropy magnetic materials. Commensurate with the divergent coercivity is an atypical drop in the temperature dependent magnetization. These effects are explained by a mixed magnetic phase model, consisting of ferro-, antiferro-, and frustrated magnetic regions, and are rationalized by simulations. A machine-learning algorithm is employed to visualize the parameter space and inform the development of subsequent compositions. Annealing the samples at 600 \ifmmode^\circ\else\textdegree\fi{}C orders the sample, more-than doubling the Curie temperature and increasing the saturation magnetization by as much as 5\ifmmode\times\else\texttimes\fi{}. Simultaneously, the large coercivities are suppressed, resulting in magnetic behavior that is largely temperature independent over a range of 350 K. The ability to transform from a hard magnet to a soft magnet over a narrow temperature range makes these materials promising for heat-assisted recording technologies.

A Practical Approach for Identification of Magnetic Fabric Carriers in Rocks

AbstractMagnetic fabric analyses of rocks by anisotropy of magnetic susceptibility (AMS) are a robust petrofabric tool that has been used in varied geological environments and tectonic settings. A fundamental difficulty of this method is to define the dominant magnetic phases and their resulting geological interpretation. We study the magnetic behavior of rocks by simulating data of mixed magnetic phases (i.e., diamagnetic, paramagnetic, and ferromagnetic). We show that it is possible to recognize the dominant magnetic phases by measuring the mean susceptibility at room temperature (kmRT) and at low temperature (kmLT). Distinct regions of magnetic phase dominancy are demonstrated in kmLT/kmRT versus kmRT and kmLT versus kmRT plots. We present a comprehensive approach by coupling the magnetic phase dominancy with possible magnetic fabrics, which are obtained from AMS measured at room and low temperatures (RT‐AMS and LT‐AMS) and anisotropy of anhysteretic remanent magnetization, into a scenario table. Application of this table allows a robust procedure for determining which magnetic phases are dominant, and permits a fast and reliable geological interpretation in complex settings.

Promoting Metamagnetic Transition by Interphase Magnetic Coupling

AbstractMagnetic mixed‐phase materials with competing ground states are important from both scientific and technical points of view due to their magnetic phase transition and phase coexistence properties. Unlike artificially fabricated multi‐phase composites, it should be possible to modify their physical properties more efficiently by making use of the interphase coupling effects in mixed‐phase materials. In this study, the magneto‐transport properties are investigated to provide evidence of the existence of interphase coupling in a magnetic mixed‐phase system, specifically, Ni‐doped FeRh thin films. The rotation of the external magnetic field induces an emergent promotion effect of the antiferromagnetic (AFM)–ferromagnetic (FM) phase transition, which can be attributed to the modification of the magnetic free energy by interphase magnetic coupling across the AFM–FM phase boundary. The results shed light on the availability of an extra degree of freedom for manipulating the physical properties of material systems with mixed magnetic phases and help to further exploit their potential applications.

Antiferromagnetism, spin-glass state, H–T phase diagram, and inverse magnetocaloric effect in Co2RuO4

Static and dynamic magnetic properties of normal spinel Co2RuO4 = (Co2+) are reported based on our investigations of the temperature (T), magnetic field (H) and frequency (f) dependence of the ac-magnetic susceptibilities and dc-magnetization (M) covering the temperature range T = 2 K–400 K and H up to 90 kOe. These investigations show that Co2RuO4 exhibits an antiferromagnetic (AFM) transition at TN ∼ 15.2 K, along with a spin-glass state at slightly lower temperature (TSG) near 14.2 K. It is argued that TN is mainly governed by the ordering of the spins of Co2+ ions occupying the A-site, whereas the exchange interaction between the Co2+ ions on the A-site and randomly distributed Ru3+ on the B-site triggers the spin-glass phase, Co3+ ions on the B-site being in the low-spin non-magnetic state. Analysis of measurements of M (H, T) for T < TN are used to construct the H–T phase diagram showing that TSG shifts to lower T varying as H2/3.2 expected for spin-glass state whereas TN is nearly H-independent. For T > TN, analysis of the paramagnetic susceptibility (χ) vs. T data are fit to the modified Curie–Weiss law, χ = χ0 + C/(T + θ), with χ0 = 0.0015 emu mol−1Oe−1 yielding θ = 53 K and C = 2.16 emu-K mol−1Oe−1, the later yielding an effective magnetic moment μeff = 4.16 μB comparable to the expected value of μeff = 4.24 μB per Co2RuO4. Using TN, θ and high temperature series for χ, dominant exchange constant J1/kB ∼ 6 K between the Co2+ on the A-sites is estimated. Analysis of the ac magnetic susceptibilities near TSG yields the dynamical critical exponent zν = 5.2 and microscopic spin relaxation time τ0 ∼ 1.16 × 10−10 sec characteristic of cluster spin-glasses and the observed time-dependence of M(t) is supportive of the spin-glass state. Large M–H loop asymmetry at low temperatures with giant exchange bias effect (HEB ∼ 1.8 kOe) and coercivity (HC ∼ 7 kOe) for a field cooled sample further support the mixed magnetic phase nature of this interesting spinel. The negative magnetocaloric effect observed below TN is interpreted to be due to the AFM and SG ordering. It is argued that the observed change from positive MCE (magnetocaloric effect) for T > TN to inverse MCE for T < TN observed in Co2RuO4 (and reported previously in other systems also) is related to the change in sign of (∂M/∂T) vs. T data.

Investigation of NiO reduction dynamics and properties of NiO-Ti powders

Abstract A detailed study of the mechanochemical (MC) processing of NiO-Ti [NiO-Ti (x at.%) with x = 20, 35] powders was carried out using a high-energy ball milling technique to investigate the formation of a NiO-based nanocomposite as a function of the milling time. During milling, the reduction of NiO to Ni follows a gradual process with a reduction of 10% and a self-sustaining process with a maximum reduction of 94% for x = 20 and 35 powders, respectively. The types of NiO reduction and the formation of ferromagnetic (FM) Ni from NiO could be accounted for by the change in magnetization to maximum values of 2 emu/g and 24 emu/g for the gradual and self-sustaining reactions, respectively. The relative fractions of Ni and NiO phases play an important role in (i) the formation of FM nanocomposite, (ii) the enhancement of magnetic anisotropy caused by the coexistence of mixed magnetic phases, (iii) temperature-induced structural phase changes and (iv) the gradual decrease in the induced FM phase with the increase in milling time. The process of time-dependent MC reduction and the resulting structural, vibrational and magnetic behavior of the in situ FM nanocomposite were studied in detail. This process may reveal potential applications in metallurgy and ore reduction processes.

Phase boundary exchange coupling in the mixed magnetic phase regime of a Pd-doped FeRh epilayer

Spin-wave resonance measurements were performed in the mixed magnetic phase regime of a Pd-doped FeRh epilayer that appears as the first-order ferromagnetic-antiferromagnetic phase transition takes place. It is seen that the measured value of the exchange stiffness is suppressed throughout the measurement range when compared to the expected value of the fully ferromagnetic regime, extracted via the independent means of a measurement of the Curie point, for only slight changes in the ferromagnetic volume fraction. This behavior is attributed to the influence of the antiferromagnetic phase: inspired by previous experiments that show ferromagnetism to be most persistent at the surfaces and interfaces of FeRh thin films, we modelled the antiferromagnetic phase as forming a thin layer in the middle of the epilayer through which the two ferromagnetic layers are coupled up to a certain critical thickness. The development of this exchange stiffness is then consistent with that expected from the development of an exchange coupling across the magnetic phase boundary, as a consequence of a thickness dependent phase transition taking place in the antiferromagnetic regions and is supported by complimentary computer simulations of atomistic spin-dynamics. The development of the Gilbert damping parameter extracted from the ferromagnetic resonance investigations is consistent with this picture.

Magnetic nano-carbon core shell as potent mixed hemimicelle solid phase extraction strategy for determination of acrylamide from potato chips coupled by high-performance liquid chromatography

Magnetic nano-carbon core shell was applied as mixed hemimicelle magnetic solid phase extraction adsorbent to introduce a novel sample preparation method for determination of acrylamide from potato chips. Acrylamide is identified as neurotoxic, a probable human carcinogen (group 2A) compound. Effective extraction parameters such as type and amount of extracting solvent, type and amount of adsorbent, time of extraction and desorption, the effect of pH, time of ionic liquid loading on the adsorbent and stirring rate (rpm) were studied and optimized. Under optimized extraction conditions, a good linearity was observed in the concentration range of 100–1500 ng/g. Limit of detection was observed as 30 ng/g. Application of the proposed method was surveyed by analysis of some potato chips brands available in the local supermarkets. The satisfactory results with the recovery of 95.58% revealed that the proposed method could be applied in food analysis laboratories.

Presence of mixed magnetic phase in mechanically milled nanosized Co0.5Zn0.5Fe2O4: A study on structural, magnetic and hyperfine properties

Abstract In this paper, we have presented a detailed study on the effects of mechanical activation caused by high energy ball milling on the structural, magnetic and hyperfine properties of nanosized Co0.5Zn0.5Fe2O4 having three different particle sizes 63 (M1), 25 (M2) and 17 nm (M3) synthesized by chemical coprecipitation method. Characterization techniques like powder x-ray diffraction, high resolution transmission electron microscopy, dc magnetic measurements and Mossbauer spectroscopic techniques have been employed to examine M1, M2 and M3 thoroughly. All the three samples are cubic spinel ferrites with Fd 3 - m symmetry. The lattice parameters of M1, M2 and M3 are 8.395, 8.391 and 8.375 A, respectively. The particles constituting all the three samples possess both superparamagnetic and ferrimagnetic phases at room temperature. The values of blocking temperature of M1, M2 and M3 are 204, 210 and 220 K, respectively. The values of saturation magnetization of M1, M2 and M3 at 300 and 10 K are 56.8, 55.3, 51.5 emu g−1 and 115.68, 113.84, 109.65 emu g−1, respectively. The values of coercivity for M1, M2 and M3 at 10 K are 1395, 2190 and 1950 Oe, respectively. The theory of magnetic domains has been exploited to explicate the trend in coercivity. The cation distribution of M2 is (Zn2+0.48Fe3+0.52)A[Co2+0.5Zn2+0.02Fe3+1.48]BO4. The effects of mechanical activation on cation redistribution and magnetic property of M2 have been investigated by infield Mossbauer spectroscopic measurements and verified by theoretical analysis of experimental results of Rietveld refinement of powder x-ray diffraction data in conjugation with dc magnetic study. The sample M2 is basically ferrimagnetic in nature possessing a slightly canted core surrounded by a disordered shell. It exhibits excellent memory effect in its dc magnetization measurement. The sample is capable of encoding, preserving and recalling binary numbers through magnetic field change. This property of the sample may be used to design magnetic coding and sensing devices.

Development of half metallicity within mixed magnetic phase of Cu1−xCoxMnSb alloy

Cubic half-Heusler Cu1−xCoxMnSb () compounds have been investigated both experimentally and theoretically for their magnetic, transport and electronic properties in search of possible half metallic antiferromagnetism. The systems (Cu,Co)MnSb are of particular interest as the end member alloys CuMnSb and CoMnSb are semi metallic (SM) antiferromagnetic (AFM) and half metallic (HM) ferromagnetic (FM), respectively. Clearly, Co-doping at the Cu-site of CuMnSb introduces changes in the carrier concentration at the Fermi level that may lead to half metallic ground state but there remains a persistent controversy whether the AFM to FM transition occurs simultaneously. Our experimental results reveal that the AFM to FM magnetic transition occurs through a percolation mechanism where Co-substitution gradually suppresses the AFM phase and forces FM polarization around every dopant cobalt. As a result a mixed magnetic phase is realized within this composition range while a nearly HM band structure is developed already at the 10% Co-doping. Absence of T2 dependence in the resistivity variation at low T-region serves as an indirect proof of opening up an energy gap at the Fermi surface in one of the spin channels. This is further corroborated by the ab initio electronic structure calculations that suggests that a nearly ferromagnetic half-metallic ground state is stabilized by Sb-p holes produced upon Co doping.

Mixed hemimicelle solid-phase extraction based on magnetic halloysite nanotubes and ionic liquids for the determination and extraction of azo dyes in environmental water samples

An effective and greener mixed hemimicelles magnetic solid phase extraction (MHMSPE) based on magnetic halloysite nanotubes (MHNTs) and ionic liquid (IL) is developed for the simultaneous enrichment and determination of anionic azo dyes in a spiked environmental water sample. In this MHMSPE, the formation of C16mimBr with mixed hemimicelles on the surface of MHNTs leads to the retention of analytes by strong hydrophobic, p-p and electrostatic interactions. This MHMSPE technique combines the advantages of MHNTs and mixed hemimicelles. Zeta potential data demonstrated that mixed hemimicelles were formed in [C16mimBr]/[MHNTs] ratios of the range from 0.15 to 1.33. Different important factors affecting the preconcentration of analytes were investigated and optimized by response surface methodology and one variable at a time. Under the optimum conditions, the limits of detection (LOD) for methyl red and methyl orange (MR and MO) were 0.042 and 0.050 μg L−1 in samples, respectively. The accuracy of the method was assessed by recovery measurements on a spiked sample, and good recoveries 85–87% for MR and 89–93% for MO, with preconcentration factors of 481 and 524, respectively. The low relative standard deviations from 1.6–3.1% for tap water and 2.5–5.4% for lake water was achieved. So far as we know, this is the first development of a mixed hemimicelles SPE based on MHNTs and IL for the extraction of trace anionic azo dyes in environment water samples.

Tailoring magnetic domains in Gd-Fe thin films

This paper presents the global modification of magnetic domains and magnetic properties in amorphous Gd19Fe81 thin films with rapid thermal processing at two distinct temperatures (250oC and 450oC), and with different time intervals viz., 2, 5, 10 and 20 minutes. 100 nm thick as-prepared films display nano-scale meandering stripe domains with high magnetic phase contrast which is the signature of perpendicular magnetic anisotropy. The films processed at 250oC for various time intervals show successive reduction in magnetic phase contrast and domain size. The domain pattern completely disappeared, and topography dominated mixed magnetic phase has been obtained for the films processed at 450oC for time intervals greater than 2 minutes. The magnetization measurements indicate the reduction in perpendicular magnetic anisotropy with increase in saturation magnetization for all the rapid thermal processed films. The experimental outputs have been used to simulate the domain pattern. Reduction in uniaxial anisotropy along with the increase in saturation magnetization successfully explain the experimental trend of decrease in domain size and magnetic contrast.

Mechanical activation on aluminothermic reduction and magnetic properties of NiO powders

We report the mechanically activated aluminothermic reduction of NiO [NiO–Al(x wt.%) with x = 0, 20, 40] into NiO–Ni–Al2O3 nanocomposites using high-energy planetary ball milling under dry milling and the resulting structural and magnetic properties. Structural studies reveal that both NiO and NiO–Al powders exhibit a face centered cubic structure with large crystal size reduction. However, the NiO–Al milled powders unveil the process of aluminothermic reaction kinetics, which changes from gradual reaction as a function of milling time for x = 20 powders to self-propagating combustion reaction for x = 40. This allows us to achieve a maximum NiO reduction of 40% and 90% for x = 20 and 40, respectively. The process of NiO reduction by Al is further confirmed through thermal studies. Pure NiO shows an antiferromagnetic (AFM) nature, which transforms into a ferromagnetic (FM) one with the moderate magnetization of about 1 emu g−1 with decreasing crystal size. The formation of FM Ni from AFM NiO matrix in milled NiO–Al powders could be precisely monitored by the change in the magnetization, which increases up to 4 emu g−1 and 28 emu g−1 for the gradual and combustion reactions, respectively. This results in a considerable exchange bias and its magnitude strongly depends on the relative fractions of NiO and Ni phases. Thermomagnetization data confirm the presence of mixed magnetic phases and the component of induced FM phase fades out due to the formation of Ni from the reduction of NiO. The changes in the structural and magnetic properties of milled NiO–Al powders are discussed on the basis of milling time-dependent mechanically activated reduction reaction of NiO into NiO–Ni–Al2O3 nanocomposites. The process of mechanical activation on the aluminothermic reduction allows for a controlled reduction of NiO; thus, it is suitable for the applications in catalysis and the ore reduction process.

Mixed magnetic exchange interactions and ferromagnetic diffuse phase transition of La1−xMnO3+δ manganites

Effects of vacancy on the microstructural and magnetic properties in self-doped La[Formula: see text]MnO[Formula: see text] [Formula: see text] manganites have been studied. The samples crystallize in a single phase of rhombohedral structure exhibiting R[Formula: see text]C space group until [Formula: see text]-value reaches 0.2. As self-doped concentration increases, structural distortion is confirmed by combining X-ray diffraction. Ferromagnetic (FM) and antiferromagnetic (AFM) coupling is found and exchange bias effect appears at low temperature. Ferromagnetic diffuse phase transition (FDPT) is induced by Griffiths phase for [Formula: see text] at temperature of [Formula: see text]. The FM transition temperature range is increased from 32 K to 150 K. The enhancement of Griffiths phase with [Formula: see text] for [Formula: see text] is explained by the greater [Formula: see text]-site spatial disorder and the structural distortion.

Nature of electron correlation and hybridization in NixCu1−xMnSb Heusler alloys

The electronic structure of Heusler alloys having mixed magnetic phases, comprising of vicinal anti-ferromagnetic and ferromagnetic orders, is of great significance. We present the results of an electronic structure study on NixCu1−xMnSb Heusler alloys, using Mn-2p core-level photoemission spectroscopy. Room temperature data in the paramagnetic phase reveal a non-monotonic variation of both electron correlation strength and conduction-band hybridization such that the former enhances while the latter weakens for compositions showing a mixed phase relative to compositions at the phase boundaries to the ordered phases. The results suggest a possible electronic driving force for settling mixed-magnetic phases.