Ferromagnetic Transition Temperature Tc Research Articles

Investigation of Magnetocaloric Effect and Critical Field Analysis of Nd0.7−xLaxSr0.3MnO3 (x = 0.0−0.3) Manganites

This research explored the temperature dependence magnetization, magnetocaloric effect, and critical field analysis of Nd0.7−xLaxSr0.3MnO3 (x = 0.0, 0.1, 0.2 and 0.3) manganites samples synthesized through solid state reaction route. The substitution of La3+ at Nd3+ site enhances the A-site average ionic radius ( rA ) from 1.321 Å (for x = 0.0) to 1.348 Å (for x = 0.3). An increase in rA reduced the internal chemical pressure inside the lattice such that the Mn–O–Mn bond angle approached 180°. In addition, an increase in Mn–O–Mn bond angle supresses the spin-lattice interaction, which consequently reduces the change in maximum magnetic entropy (ΔSMmax) at the magnetic transition temperature. This implies that variation of A-site average ionic radius influences the change in maximum magnetic entropy. The critical behavior of the manganite samples was addressed based on the data of magnetization measurements around the transition temperature TC. Various techniques such as modified Arrott plot, a Kouvel–Fisher method, and critical isotherm analysis were used to measure the values of the ferromagnetic transition temperature TC, as well as the critical exponents of β, γ, and δ. The magnetic order parameter n is very well obeyed with scaling relation with change in magnetic entropy.

Near-room temperature ferromagnetism and a tunable anomalous Hall effect in atomically thin Fe4CoGeTe2.

Itinerant ferromagnetism at room temperature is a key factor for spin transport and manipulation. Here, we report the realization of near-room temperature itinerant ferromagnetism in Co doped Fe5GeTe2 thin flakes. The ferromagnetic transition temperature TC (∼323 K-337 K) is almost unchanged when the thickness is as low as 12 nm and is still about 284 K at 2 nm (bilayer thickness). Theoretical calculations further indicate that the ferromagnetism persists in monolayer Fe4CoGeTe2. In addition to the robust ferromagnetism down to the ultrathin limit, Fe4CoGeTe2 exhibits an unusual temperature- and thickness-dependent intrinsic anomalous Hall effect. We propose that it could be ascribed to the dependence of the band structure on thickness that changes the Berry curvature near the Fermi energy level subtly. The near-room temperature ferromagnetism and tunable anomalous Hall effect in atomically thin Fe4CoGeTe2 provide opportunities to understand the exotic transport properties of two-dimensional van der Waals magnetic materials and explore their potential applications in spintronics.

Nanostructured double perovskite magnetic thin films by PLD

Semi-metallic ferromagnetic oxides, having a double perovskite structure, exhibit a variety of strange magneto transport and magnetic characteristics for spintronics applications. The double perovskites Sr2FeMoO6 (SFMO) and Sr2FeWO6 (SFWO) are known as potential magneto resistive materials that exhibit appreciable tunnel-type intrinsic magnetoresistance (TMR) at room temperature. Current research is focused on the deposition and characterization of nanocrystalline thin layers of SFMO and SFWO materials on LaAlO3 substrate with a temperature of 825 °C and pressure of 0.03 mTorr using the pulsed laser deposition (PLD) method. Films are nearly single-crystalline with a predominant c-axis orientation. A smaller peak corresponding to the plane (101) at 2θ = 19.6° was also found, indicating the arrangement of Fe, and Mo ions at B and B' locations in samples. Atomic Force Microscope (AFM) studies reflect uniform grain growth with surface roughness and average grain size of approximately 8 nm and 52.6 nm; 6 nm and 28.2 nm, respectively for SFMO and SFWO thin films. Magnetization measurement at 5 K shows that SFMO is ferromagnetic and SFWO is antiferromagnetic with a significant difference in their magnetic moments. M−T curve of the SFWO film shows a peak at 36.7 K, resembling the Neel temperature. While the M−T graph of SFMO thin films reveals that ferromagnetic transition temperature (Tc) is higher than 320 K.

Influence of Y substitution on structural, magneto-transport, and magnetic properties of La2-xYxCoMnO6 (0 ≤ x ≤ 0.3) double perovskites

We report a comprehensive study on the correlations of structural, magnetic, and electronic properties of Y substituted double perovskite La2-xYxCoMnO6 (0 ≤ x ≤ 0.3) compounds. The Rietveld refined X-ray diffraction patterns reveal that all synthesized compounds crystallize in monoclinic structure with the P21/n space group. Raman spectra affirm the presence of well-defined bands, assigned to the double perovskite structure. The temperature dependence of electrical resistivity indicates the semiconducting nature of the compounds without any transition and is effectively probed by Variable range hopping model. The application of a magnetic field suppresses the resistivity to exhibit significant low-temperature magnetoresistance. The paramagnetic to ferromagnetic transition temperature (Tc) decreased but saturation/remnant magnetization increased with increasing Y doping. The effective magnetic moments determined by the Curie-Weiss law show a decrease in the Y concentration. The substitution of iso-valent Y at the La site induces structural compression which is strongly correlated to the enhancement of effective magnetization values.

A DFT+U study of site dependent Fe-doped TiO2 diluted magnetic semiconductor material: Room-temperature ferromagnetism and improved semiconducting properties

This article reports the crystal structure, impurity formation energy, electronic property, magnetic property, and dopant configuration site dependence of ferromagnetic temperature Tc of anatase (Ti15FeO32, Ti14Fe2O32, and Ti13Fe3O32) by first-principles calculations based on density functional theory (DFT) with Hubbard onsite correction (DFT+U). The estimated formation energy validated the structural stability of the Fe-doped TiO2 with 2.08% (Ti15FeO32), 4.17% (Ti14Fe2O32), and 6.25% (Ti13Fe3O32) concentrations at the Ti sites. The electronic structure analysis reveals that the bandgap in the doped system changed from a wide bandgap of 3.23 eV (pristine TiO2) to slightly lower bandgaps of 3.13, 3.08, and 3.04 eV with Fe concentrations of 2.08%, 4.17%, and 6.25%, respectively. The calculated partial density of states also show the hybridization of O with 2p- and Fe 3d-orbitals near the conduction band minimum and generate the impurity energy level reducing the bandgap. Furthermore, the estimated Curie temperature (Tc) varied depending on the Fe–Fe interactions, the concentration of the Fe dopants, and doping sites. For instance, Tc is calculated to be 343.57 K for 2.08% Fe at the symmetric point of the crystal while estimated to be 323.84 and 393.297 K for 4.17% at the nearest neighbor and the next-nearest neighbor configurations. Due to the increase of the Fe concentration to 6.25%, the calculated Tc monotonically improved to 342.5 and 513.174 K at the nearest neighbor and the next-nearest neighbor of the Fe-site, respectively. These indicate that all the calculated findings estimate the ferromagnetic transition temperature Tc to above room temperature. Moreover, the system’s total magnetization reveals the augmentation of a number of unpaired electrons as a result of rise in oxygen vacancies and, hence, there could be more holes when the Fe content gets higher, perhaps generating more bound magnetic polarons that favor the critical temperature, Tc.

First-Principles Investigation of Structural, Electronic, and Room Temperature Ferromagnetism in Si-Doped Monolayer BN

We performed spin-polarized density functional theory (DFT) to investigate the structural, electronic, and magnetic properties of silicon- (Si-) doped monolayer boron nitride (BN). The present study revealed that structural parameters like bond length, bond angle, and lattice parameters increase as Si-doped in the B site of monolayer BN. However, the bandgap of monolayer BN is reduced in the presence of the Si dopant. Moreover, the obtained magnetic moment and analysis of the total density of states (TDOS) show that Si-doped monolayer BN displays ferromagnetism. The calculated ferromagnetic transition temperature (Tc) value for Si concentration of 12.5% is 476 K which exceeds room temperature. The findings are avenues to enhance the application of monolayer BN for spintronics.

Electrical transport properties driven by magnetic competition in hole-doped perovskite Pr1-xBaxMnO3 (0.25 ≤ x ≤ 0.36)

In this work, polycrystalline Pr1-xBaxMnO3 (0.25 ≤ x ≤ 0.36) ceramics were synthesized, and their magnetic and electrical transport properties were systematically studied. All samples show two metal-insulator transitions (MITs) corresponding to the high temperature TMI1 and low temperature TMI2, respectively, besides the non-Griffith phase above the ferromagnetic (FM) transition temperature TC. Combining the results of the transport and magnetic properties, it is found that the FM transition temperature TC coincides with the temperature TMI1, which is linearly related to the A-site ionic radius mismatch variance σ2, indicating the enhancement of FM interactions due to the increase of the degree of B-site ordering of Mn3+/Mn4+ ions. The positive correlation between ferromagnetic insulators (FMI) and magnetic interactions, including the FM and short-range antiferromagnetic (AFM) interactions, is confirmed. It is suggested that the first MIT at TMI1 is attributed to the Mn3+/Mn4+ double exchange interactions and the second MIT at TMI2 is closely related to the suppression of the AFM interactions under the internal FM field induced by the Mn3+/Mn4+ DE interactions. This work provides not only a theoretical understanding on the origin of MIT at low temperature, but also a new way for adjusting the FMI in perovskite manganese oxide Pr1-xBaxMnO3 for application.

First principles investigation of structural, electronic, and room temperature ferromagnetism in V doped hexagonal pristine graphene

The structural, electronic, and magnetic properties of V doped graphene were investigated using density functional theory. The formation energy calculation indicates that V doped graphene is stable and the V atoms are strongly hybridized with C atoms. The present study revealed that the bandgap of graphene is open in the presence of the V dopant. Moreover, the obtained magnetic moment and analysis of total density of states show that V doped graphene displays ferromagnetism. The calculated ferromagnetic transition temperature (Tc) value for a V concentration of 6.25% is 377 K. The findings are avenues to enhance the application of graphene for spintronics.

Antisite Defect and Magnetic Frustration in Double Perovskite Ln2CuRuO6 (Ln = La, Pr) Compounds

Magnetism in double perovskite oxides of the formula A2BB'O6 has been a subject of great interest and intensive research in condensed matter physics. In this paper, Ln2CuRuO6 (A = La, Pr) samples were synthesized by solid-state reaction method, and we investigated their structural and magnetic properties. The new double perovskite compound Pr2CuRuO6 stabilizes in the monoclinic P21/n structure with an antisite defect fraction of ~ 3% between Cu and Ru sites. Our structural analysis indicates the severe deformation of Cu-O-Ru bond angle, as La3+ is replaced by the smaller rare earth ion Pr3+. For Pr2CuRuO6, the observed ferromagnetic transition temperature (Tc = 32 K) is higher than that of La2CuRuO6 (Tc = 15 K), which may be possibly associated with the enhanced magnetic interaction due to the distorted Cu-O-Ru bond angle. In addition, the anomalous phenomenon of ZFC susceptibility at low temperature suggests a degree of magnetic frustration and can be attributable to the intrinsic antisite defect in Pr2CuRuO6. The first principle calculations confirm a ferromagnetic Cu-Ru exchange interaction in Pr2CuRuO6, which is different from the antiferromagnetic case for La2CuRuO6.

Magnetic Properties of Eu8GaxGe46−x (Nominal x = 16, 14, and 12) Type-I Clathrates

Melt-spinning technique can widen the range of Ga content in Eu8GaxGe46−x type-I clathrate. In this paper, it was used to obtain Eu8GaxGe46−x with nominal 16 ≥ x ≥ 10. Three samples with nominal x = 16, 14, and 12 are discussed in detail. Their actual Ga contents detected by EDS are 14.3, 13.4, and 11.5, which is a relatively wide range that has not been reported before. The decrease of Ga content results in the decrease of lattice parameter a. Moreover, a huge decline of the ferromagnetic transition temperature TC is observed. It is 34.7 K, 27.0 K, and 20.0 K for Eu8GaxGe46−x with nominal x =16, 14, and 12, respectively. However, the saturation magnetic moment μsat and effective magnetic moment μeff are not greatly affected by the change of Ga content. The decrease of TC is mainly attributed to the decrease of molecular field coefficient λ, which can be calculated by fitting the relation curve between exchange mean field Hexch and magnetization M. The fitted λ values are 0.25, 0.18, and 0.16 for samples with nominal x = 16, 14, and 12. Because the decrease of TC is beneficial to the increase of magnetic entropy change, the maximum value of magnetic entropy change ( $$ - \Delta S_{{_{\text{M}} }}^{ \text{max} } $$ ) around TC when $$ \Delta H $$ = 3 T increases from 6.0 to 7.0 J/(kg K) as x decreases from 16 to 12.

Tuning the magneto-electrical properties of multiferroic multilayers through interface strain and disorder

Artificially engineered superlattices were designed and fabricated to induce different growth mechanisms and structural characteristics. DC sputtering was used to grow ferromagnetic (La0.8Ba0.2MnO3)/ferroelectric (Ba0.25Sr0.75TiO3 or BaTiO3) superlattices. We systematically modified the thickness of the ferromagnetic layer to analyze dimensional and structural disorder effects on the superlattices with different structural characteristics. The crystalline structure was characterized by X-ray diffraction and transmission electron microscopy. The magnetic and electronic properties were investigated by SQUID magnetometry and resistance measurements. The results show that both strain and structural disorder can significantly affect the physical properties of the systems. Ba0.25Sr0.75TiO3 based superlattices with a low thickness of the ferromagnetic layers (4 nm) present compressive strain that decreases the ferromagnetic transition temperature from 250 K corresponding to the unstressed samples to 230 K. In these samples, the localization energy of the charge carrier through the electron-phonon interaction decreases at low temperatures (∼100 meV). Ba0.25Sr0.75TiO3 based superlattices with thicknesses of the ferromagnetic layers higher than 12 nm present tensile strain that reduces the charge carrier localization energy at low temperatures (∼1 meV), increasing the ferromagnetic transition temperature (Tc∼265 K). Structural defects in BaTiO3 based superlattices have a stronger influence on the magnetic properties than on the transport properties. Nevertheless, disorder blocks the ferromagnetic transition for highly disordered samples (thickness of the ferromagnetic layer < 3 nm). These results help to further understand the role of strain and interface effects in the magnetic and transport properties of manganite based multiferroic systems.

Possible Tricritical Behavior and Anomalous Lattice Softening in van der Waals Itinerant Ferromagnet Fe3GeTe2 under High PressureSupported by the National Key Research and Development Program of China (Grant Nos. 2018YFA0305704 and 2016YFA0401804), the National Natural Science Foundation of China (Grant Nos. 11774352, U1832214, U19A2093, 11804344, U1632275, 11874362, 11704387, and U1932152), the Users with Excellence Project of Hefei Center CAS (Grant

We present a high-pressure study of van der Waals ferromagnetic metal Fe3GeTe2 through electrical transport and Raman scattering measurements in diamond anvil cells at pressures up to 22.4GPa. Upon compression, the ferromagnetic transition temperature Tc manifested by a kink in resistance curve decreases monotonically and becomes undiscernable around Pc = 10GPa, indicative of suppression of the itinerant ferromagnetism. Meanwhile, by fitting the low temperature resistance to the Fermi liquid behavior of R = R0 + AT2, we found that R0 shows a cusp-like anomaly and the coefficient A diverges around Pc. These transport anomalies imply a tricritical point as commonly observed in itinerant ferromagnets under pressure. Unexpectedly, the Raman-active E2g and A1g modes soften remarkably after an initial weak hardening and the peak widths of both modes broaden evidently on approaching Pc, followed by complete disappearance of both modes above this critical pressure. A possible underlying mechanism for such anomalous lattice softening near Pc is discussed.

Anomalous magnetism in Al doped La2CoMnO6 ceramics

La2CoMn1-xAlxO6 (0 ≤ × ≤ 1.00) samples were synthesized by sol–gel method, and their crystal structure and magnetic properties were investigated. X-ray diffraction reveals a structural transition from monoclinic (space group P21/n) to rhombohedral phase (space group R-3c) with Al content increasing. As envisionedandexpected, the remanent magnetization Mr and ferromagnetic (FM) transition temperature TC dramatically decrease with the increment of Al doping, which is due to the destruction of the long-range Co2+-O-Mn4+ FM super-exchange interaction induced by Al ion doping. However, abnormally increase of coercive field HC and effective magnetic moment μeff appear for × = 0.25. The results of infrared spectrum, Raman spectrum, and X-ray photoelectron spectroscopy illustrate that this anomaly can be attributed to the spin-state transition of Co3+ ions from intermediate spin (IS) to high spin (HS) state with × increasing to 0.25, rather than the valence changes of the magnetic ions. This spin-state transition is probably due to the increase of crystal symmetry with high disorder and the suppression of Jahn-Teller distortion. The suppressing Jahn-Teller distortion favors the stability of the HS state of Co3+ ions.

Assessment of the critical behavior near the FM to PM phase transition in cubic Ni0.3−xCuxZn0.7Fe2O4 spinel ferrite

In this study, we report a thorough examination of the critical behavior of the cubic Ni0.3−xCux Zn0.7Fe2O4 (x = 0.0, 0.1 and 0.2) spinel ferrite which are crystallized with different irregular shapes of particle size (spherical,polygonal and cubic). The magnetic transition is ferromagnetic to paramagnetic state for all Cu-doped compounds. Different theoretical analyses, as the modified Arrott plot, Kouvel–Fisher method, and critical isotherm, have been used to identify the values of the ferromagnetic transition temperature TC, and the critical exponents of β, γ and δ. All the obtained values of critical parameters were found to be close to the 3D-Heisenberg theoretical model, which implies short-range magnetic interactions in Cu-doped compounds. The reliability of critical parameters was further checked through different methods, such as the Widom scaling relationship and the magnetic equation.

A modified piezoelectric ultrasonic composite oscillator technique for simultaneous measurement of elastic moduli and internal frictions at varied temperature.

In this work, a modified piezoelectric ultrasonic composite oscillator technique (M-PUCOT) is developed for measuring a material's elastic moduli and internal frictions, as a function of temperature. Different from the traditional PUCOT that employs two quartz bars as the drive and gauge, here, a single small piezoelectric transducer (PZT) ring is used to drive and sense longitudinal or torsional vibration in a cylinder specimen. Because of the strong piezoelectric effect and relatively large bandwidth of the PZTs compared to their quartz counterpart, the frequency match condition between the transducer and the specimen is not required in this M-PUCOT. For high temperature measurement, a fused quartz spacer, whose resonance frequency matches the specimen's, is bonded between the transducer and the specimen to provide thermal insulation. First, the united equivalent circuit of the transducer- (spacer) -specimen composite system was derived. Then, Young's modulus, longitudinal friction, shear modulus, and torsional friction were explicitly obtained by measuring the resonance frequency and antiresonance frequency of the 2- or 3-component system's electrical susceptance curve using an impedance analyzer. The accuracy of this method was validated both by measuring the system's amplitude-frequency curves using a laser vibrometer and through finite element simulations. The repeatability error of the M-PUCOT is only ∼0.2% for moduli measurement and ∼2.5% for internal friction measurement, which is very promising for studying the moduli and internal friction variations during damage, fatigue, and phase transitions. Finally, the M-PUCOT was employed to measure the variations in moduli and internal frictions of an Fe64Ni36 Invar alloy from room temperature to 500 °C. Results show that above the ferromagnetic phase transition temperature Tc, both moduli reach their maxima, and both internal frictions reach their minima. The proposed M-PUCOT is expected to be widely used in the near future for its quick measurement, high repeatability, and low cost.

Electronic Structure and Ferromagnetic Transition Temperature of Ga1– xMnxAs in the Nonempirical Local Exchange Method

Density functional theory (DFT) calculations have been used to study the band structure and density of states of a Ga1 – xMnxAs diluted magnetic semiconductor. It has been shown that some of the Mn 3d states are hybridized with the valence band at the Fermi level. Magnetic properties have been calculated by a multiscale method using DFT densities of states and exchange integrals calculated for a Mn atom by the Hartree–Fock method. The theoretical ferromagnetic transition temperature TC of Ga0.9375Mn0.0625As agrees with experimental data. spintronic materials, diluted magnetic semiconductor, GaAs, Mn, density functional method, density of states, band structure

Mn-induced Ferromagnetic Semiconducting Behavior with Linear Negative Magnetoresistance in Sr4(Ru1\u2212xMnx)3O10 Single Crystals

Triple-layered Sr4Ru3O10 is a unique ferromagnet with the central RuO6 layer behaving differently from two outer layers both crystallographically and magnetically. We report that the partial substitution of Ru by smaller Mn gives rise to modification in crystal structure, electronic and magnetic properties of Sr4(Ru1−xMnx)3O10. Through the single crystal X-ray diffraction refinement, we find that (Ru/Mn)O6 octahedral rotation is no longer detectable at x ≥ 0.23, leading to the tetragonal structure. The magnetization measurements indicate the ferromagnetic transition temperature TC decreases from 105 K for x = 0 to 30 K for x = 0.41, with the reduced magnetic moment as well. Remarkably, Mn doping results in the change of magnetic anisotropy from the easy c axis in x = 0 to the easy ab plane seen in x = 0.34 and 0.41. Such change also removes the ab-plane metamagnetic transition observed in x = 0. Furthermore, the electrical resistivity increases with increasing x showing semiconducting behavior with Δ ~ 10 meV for x = 0.34 and 30 meV for x = 0.41. Under applied magnetic field, the magnetoresistance exhibits negative and linear field dependence in all current and field configurations. These results clearly indicate Sr4(Ru1−xMnx)3O10 is a novel ferromagnetic semiconductor with exotic magnetotransport properties.

Electronic structure and nearly room-temperature ferromagnetism in V-doped monolayer and bilayer MoS2

The electronic structure, magnetic properties and ferromagnetic transition temperature (Tc) of Vandium (V) doped monolayer (ML) and bilayer (BL) MoS2 are investigated using density function theory (DFT) plus on-site Hubbard potential correction (U). The results show that substitution of V dopant atom at the Mo sites are energetically favorable and magnetic interaction between two dopants in ML and BL MoS2 oscillates from ferromagnetic (FM) to antiferromagnetic (AF) depending on atomic distance between dopants. Our result also shows that a pair of V dopants in different layers of BL MoS2 interacts antiferromagnetically. Moreover, it is obtained that interlayer interaction in BL MoS2 affects the magnetic interaction in V-doped BL MoS2. The calculated ferromagnetic transition temperatures (Tc) value for impurity concentration of 12.5% and 22.22% are 242 and 285 K, respectively, for ML phase. However, for BL phase T[Formula: see text] values are 187 and 256 K for concentration of 6.25% and 11.11%, respectively, these values are closer to room-temperature. Our calculations indicate that, V-doped ML and BL MoS2 are promising candidates for 2D dilute magnetic semiconductors for spintronics applications.

Investigation of ‘magnetic hardness’ of the grain boundary in Sr2FeMoO6 ceramics

Intrinsic spin-valve-type magnetoresistance (SVMR) behavior recently observed in Sr2FeMoO6 (SFMO) is proposed to originate from the ‘magnetic hardness’ of the insulating grain boundary. It suggests the potential for tuning the SVMR by manipulating the magnetoresistance peak position of the grain boundary with a suitable magnetic material. In this paper, CoFe2O4/Sr2FeMoO6 (CFO(x)/SFMO(100%): x = 0%–30%) composites were specifically designed by introducing the hard magnetic insulator CFO into the grain boundary of SFMO. Insulating CFO can increase the grain boundary strength (macroscopic resistivity), resulting in an enhanced low-field magnetoresistance (LFMR) of ~1.6 times with respect to the maternal SFMO. The magnetic coercivity (HC) of the CFO/SFMO grain material shows a complete enhancement which is dependent on the CFO content (x) and is due to the high magnetic anisotropy of the CFO. Vastly different from the HC response is the coercive field variance of the magnetoresistance (HC (MR)), which exhibits a complex correlation with the CFO content (x). Regardless of how much the HC (MR) changes, the SVMR behavior is still maintained because of a larger HC (MR) than that of HC when . However, almost comparable values of HC (MR) and HC are observed when x increases up to 30%, where the SVMR property is greatly destroyed. In addition, the ferromagnetic transition temperature TC values of all the samples show no obvious dependence on the CFO content (x). These interesting observations indicate that the CFO content (x) not only significantly optimizes the LFMR but it also effectively tunes the SVMR behavior. Our work may encourage further investigation of SVMR behavior in SFMO and other similar systems.

Composition dependence of transition temperatures on quaternary Co-Fe-Ni-Ga melt-spun alloys

The composition dependence of transition temperatures on quaternary Co-Fe-Ni-Ga melt-spun alloys with constant Ga content are examined. A few at.% of Fe replacement for Co in Co50Ni22Ga28 drastically reduce martensitic transformation temperature (TM) whereas ferromagnetic transition temperature (Tc) remains above 400 K. Increasing Ni instead of Co in Fe doped specimen can raise TM around room temperature again. Further increase of Fe content with this manner, the alloys finally connected to ternary Ni-Fe-Ga of ferromagnetic shape memory region. The martensitic transition start temperature (MS) of Co-Fe-Ni-Ga28 alloys show good correlation with the valence electron ratio (e/a). The MS vs e/a plot clearly shows that trend lines are separated for each Fe content, and intervals of trend lines seem to be proportional to Fe content at lower Fe region. The Tc and saturation magnetization of Co-Fe-Ni-Ga28 alloys show almost linear relation with magnetic valence Zm.