Magnetostrictive Tb Research Articles

Converse magnetoelectric effects in piezoelectric–piezomagnetic layered composites

By using the product effect of converse piezoelectric effect and piezomagnetic effect, a multilayer piezoelectric–piezomagnetic composite consisting of transversely poled piezoelectric Pb(Mg 1/3Nb 2/3)O 3–PbTiO 3 crystal layers and longitudinally magnetized magnetostrictive Tb 0.27Dy 0.73Fe 2 layers has been developed and its converse magnetoelectric (ME) effect has been studied. A wide bandwidth of the frequency peak under different magnetic bias fields was also observed. The largest value of converse ME coefficient α B at a resonance frequency of 78.6 kHz is 1.15 G/V, which is ∼10 times higher than the value at sub resonant frequencies. This composite exhibits a promising potential in the magnetic force devices electrically controlled.

Differential magnetostrictive response in magnetically annealed Tb0.36Dy0.64(Fe0.85Co0.15)2 with ⟨110⟩ crystal orientation

Magnetic heat treatment has been carried out on a giant magnetostrictive alloy Tb0.36Dy0.64(Fe0.85Co0.15)2 with ⟨110⟩ crystal orientation. A dramatic improvement in magnetostriction along and perpendicular to the crystal axis (defined as λ‖ and λ⊥, respectively) occurs when cooling the sample through the Curie temperature TC under 240kA∕m applied perpendicular to its axis. When the applied annealing field was parallel to the crystal axis, the magnetostrictive behavior becomes “anomalous;” negative λ‖ and positive λ⊥ are obtained in low fields, accompanied with relatively low values in high fields. A single-{111}-twin model has been suggested to explain such differential magnetostrictive response.

Microstructure and magnetostriction of Tb0.3Dy0.7Fe1.95 prepared under different solidification conditions by zoning and modified Bridgman techniques

An intermetallic compound of nominal composition Tb0.3Dy0.7Fe1.95 was conventionally cast in the form of cylindrical rods of 8mm diameter and directionally solidified by zoning at three different growth rates. Compounds of the same nominal composition were also directionally solidified in the form of cylindrical rods of 20mm diameter by modified Bridgman technique, at two different growth rates. The microstructure of the directionally solidified compounds has been investigated as a function of solidification rate and compared with that of conventionally cast compound. The observed microstructural features of these samples have been correlated with the magnetostriction measured on the corresponding samples. Further, by examining the longitudinal sections cut along its cylindrical axis, a correlation of microstructure with magnetostriction has been brought out for each directionally solidified sample as a function of distance from the initially solidified end to the other. It has been observed that a large magnetostriction (at 4.5kOe) and a high initial slope of magnetostriction versus applied magnetic field are realized in the directionally solidified samples as compared to the conventionally cast sample. An improvement in the property has been observed among the directionally solidified samples when solidified with higher growth rates. It is surmised on the basis of the observed microstructural features in this study that a large magnetostriction is realized if formation of (Tb,Dy)Fe2 occurs by congruent solidification rather than by the peritectic reaction L+(Tb,Dy)Fe3→(Tb,Dy)Fe2.

Structure and Magnetoelasticity of R(Zn$_1 - rm x$Fe$_rm x$) ($hboxR=hboxTb$, Dy) Polycrystalline Alloys

The structure, magnetization, and magnetostriction of R(Zn1-x Fex)(R=Tb, Dy) polycrystalline alloys were investigated by X-ray diffraction, vibrating sample magnetometry, and standard strain gauge techniques. It was found that TbZn1-xFex consists of a single Tb(Zn,Fe) phase with the cubic CsCl-type structure when x les 0.2. DyZn1-xFex was found to consist of nearly a single Dy(Zn,Fe) phase in the range 0 les x les 0.15. A second Dy-rich phase appears when x > 0.15. The Curie temperature of the RZn1-xFex alloys increases with increasing Fe content when x les 0.2. When Fe is substituted for Zn in RZn compounds, the magnetization increases with increasing Fe content. The magnetostriction of Tb(Zn1-xFex) alloys increases with increasing Fe content when x les 0.1, and that of Dy(Zn1-x Fex) alloys increases in the composition range 0 les x les 0.05

Direct experimental evidence for anisotropy compensation between Dy3+ and Pr3+ ions

Experimental evidence for the anisotropy compensation between Dy3+ and Pr3+ ions has been observed directly by performing x-ray diffraction on magnetic-field aligned powders and by evaluating the spin-reorientation temperature and the magnetostriction of Tb0.2Dy0.8−xPrx(Fe0.9B0.1)1.93 alloys. The spin-reorientation temperature decreases with increasing the Pr content. The easy magnetization direction (EMD) at room temperature of the alloys rotates continuously in the (11¯0) plane from ⟨001⟩ for x=0.18 to ⟨111⟩ for x=0.40, subjected to the anisotropy compensation between Dy3+ and Pr3+ ions. It is observed that the EMD of some of the alloys lies along nonmajor axes at room temperature. A maximum value of magnetostriction is achieved at x=0.22, which is also attributed to the anisotropy compensation.

Magnetomechanical damping capacity of Tb0.36Dy0.64(Fe1−xTx)2 (T=Co,Mn) alloys

The magnetomechanical damping capacity of the giant magnetostrictive Tb0.36Dy0.64(Fe1−xTx)2 (x=0, 0.05, 0.10; T=Mn or Co) alloys has been calculated from quasistatic strain-stress hysteresis loops at room temperature. Stress ranges from 0 to 10, 20, 30, and 50MPa were used in a series of applied fields between 0 and 3250Oe. The largest damping capacities were obtained at zero field with values of 1.14 for Tb0.36Dy0.64Fe2, 1.62 for Tb0.36Dy0.64(Fe0.95Mn0.05)2, and 1.84 for Tb0.36Dy0.64(Fe0.90Co0.10)2, respectively. In low fields, the damping capacity ΔW∕W decreases drastically with the applied stress and magnetic field. However, in higher fields, ΔW∕W decreases slightly with the magnetic field but only increases slightly with the applied stress. The results show that both Mn and Co as substitutes for Fe are beneficial for obtaining higher damping capacity.

Influence of TbDyFe film on giant magnetoimpedance in sandwiched films

The Ni80.2Fe14.1Si0.2Mn0.4Mo5.1 sandwiched films are prepared on the magnetostrictive (Tb0.27Dy0.73)0.3Fe0.7 film substrate. Due to magnetostrictive stress effect on magnetic anisotropy which is believed to be critical for the giant magneto-impedance (GMI) effect, the GMI ratio is seen to increase sharply in the magnetic fields. The GMI effect also increases when the samples are annealed at 280℃. But the GMI ratio is still less than that of the as-deposited films.

Effects of oblique deposition on magnetostrictive characteristics of TbFe 2 films formed by ion plating

The effects of oblique deposition to induce high magnetostrictive susceptibility and huge magnetostriction were studied. The giant magnetostrictive Tb–Fe films were prepared by an ion plating process with inclined vapor flux using substrates angled with 0, 30 and 60°. Increasing the substrate angle induced strongly in-plane magnetic anisotropy by the oblique deposition. The magnetic and magnetostrictive characteristics of Tb–Fe films were effected by an oblique anisotropy. The oblique anisotropy of Tb–Fe film may be induced by the shape anisotropy connected with columnar grain.

Anomalous thermal expansion and magnetostriction of rare earth compounds under high pressure

The thermal expansion coefficients of Kondo compounds, CeBe 13 and CeRh 2Si 2, and the magnetostriction of Tb 0.3Dy 0.7Fe 2(Terfenol-D) have been measured at high pressure. By simple analysis using thermodynamical relation, it is found that the density of state at the Fermi level and the Grüneisen parameters Γ of the Kondo compounds decrease rapidly with increasing pressure corresponding to the large pressure-induced enhancement of Kondo temperatures. An anomalous behaviour in the thermal expansion coefficients of CeRh 2Si 2 is observed at high pressure above T N . This anomaly is suggested as an origin of pressure-induced superconductivity. The giant magnetostriction (GMS) of Terfenol-D is found to be enhanced by applying hydrostatic pressure below 0.5 GPa but GMS decreases above it. These results are discussed briefly by comparing with the previous ones.

Strong flexural resonant magnetoelectric effect in Terfenol-D∕epoxy-Pb(Zr,Ti)O3 bilayer

We report the bending resonant magnetoelectric effect observed in the bilayer of magnetostrictive Tb0.30Dy0.7Fe2 (Terfenol-D)∕epoxy and piezoelectric Pb(Zr0.52Ti0.48)O3 (PZT). It has been found that the bilayer has both giant magnetoelectric voltage coefficient and high coupling efficiency when it operates at the first bending resonance mode. The maximum bending resonant magnetoelectric voltage coefficient of 14.6V∕cmOe at quite low frequency of 12.5 kHz was observed in the bilayer of small sizes of 17.4×4.0×1.44mm3. This bending-resonance-type magnetoelectric effect shows promising application in transducers for magnetoelectric energy conversion.

The Co-doped Tb 0.36Dy 0.64Fe 2 magnetostrictive alloys with a wide operating temperature range

Magnetostrictive alloys with a wide operating temperature range from −80 to 150 °C were developed by changing the Tb/Dy ratio of Tb x Dy 1− x Fe 2 from 0.3/0.7 to 0.36/0.64 and Co partly substituting for Fe. The structure, Curie temperature, AC susceptibility, magnetization, magnetocrystalline anisotropy constant K 1 and magnetostriction of Tb 0.36Dy 0.64(Fe 1− y Co y ) 2 ( y = 0.0 , 0.1, 0.2) alloys were investigated. It was found that the matrix of Tb 0.36Dy 0.64(Fe 1− y Co y ) 2 alloys keeps the MgCu 2-type cubic Laves structure with a small amount of R-rich phase. A small amount of R 2(Fe,Co) phase was also detected when y = 0.2 . The Curie temperature T c of Tb 0.36Dy 0.64(Fe 1− y Co y ) 2 alloys is higher than Tb 0.3Dy 0.7Fe 2 and increases drastically with increasing Co content from 387.1 °C for Tb 0.36Dy 0.64Fe 2 to 416.7 °C for Tb 0.36Dy 0.64(Fe 0.9Co 0.1) 2 and 433.3 °C for Tb 0.36Dy 0.64(Fe 0.8Co 0.2) 2. The spin reorientation temperature T r decreases from −12 °C for Tb 0.3Dy 0.7Fe 2 to −94 °C for Tb 0.36Dy 0.64Fe 2. It increases slightly with increasing Co content. The magnetocrystalline anisotropy coefficient K 1 of Tb 0.36Dy 0.64(Fe 1− y Co y ) 2 alloys is greater than Tb 0.3Dy 0.7Fe 2 but decreases with increasing Co content. The saturation magnetization M s of Co-doped alloys is lower than that of Tb 0.3Dy 0.7Fe 2 and decreases with increasing Co content. The magnetostriction of Tb 0.3Dy 0.7Fe 2 and Tb 0.36Dy 0.64(Fe 1− y Co y ) 2 alloys was examined against applied magnetic field up to 5 kOe in the temperature range from −80 to 150 °C.The temperature coefficient of magnetostriction ( Δ λ / Δ T ) of Tb 0.3Dy 0.7Fe 2 and Tb 0.36Dy 0.64(Fe 1− y Co y ) 2 alloys was also calculated by linearly simulating the magnetostriction-temperature curve, showing that the absolute value of Δ λ / Δ T at 5 kOe magnetic field is 1.17 ppm/°C for y = 0.1 and 1.35 ppm/°C for y = 0.2 , smaller than that of Co free samples, which is 2.43 ppm/°C for Tb 0.36Dy 0.64Fe 2.

The magnetostriction of Tb, Dy and Ho revisited

In this paper we present re-analyses of magnetostriction measurements earlier performed in terbium, dysprosium and holmium single crystals. In the framework of the standard theory of single-ion crystal-electric-field and two-ion exchange magnetostrictions, we explain the thermal variation of the anisotropic saturation magnetostriction within the basal plane by considering high-order terms in the magnetoelastic energy. Using complementary basal-plane magnetic anisotropy measurements, we have been able to obtain the second- and fourth-order magnetoelastic coupling parameters associated with the orthorhombic distortion of the hexagonal plane for the above-mentioned three heavy rare earths.

Effect of heat treatment on the magnetostrictive properties of Tb0.3Dy0.7Fey for 1.4 ≤ y ≤ 1.7

AbstractThe effect of annealing on the microstructure and magnetostriction of Tb0.3Dy0.7Fey for 1.4 ≤ y ≤ 1.7 was investigated. As the y value decreased, the volume fraction of the eutectic phase increased and this phase leaked out from a sample during annealing above the eutectic temperature, which significantly changed the magnetostrictive properties. We compare the effects of leakage of the eutectic phase and annealing on the magnetostriction and discuss the reasons.

Structure and magnetostriction of Tb 1− xPr xFe 1.93B 0.15 alloys

Structure, magnetic properties and magnetostriction of Tb 1− x Pr x Fe 1.93B 0.15 (0⩽×⩽0.8) alloys are investigated. Addition of a small amount of boron and extra rare earth is beneficial to the formation of a single Laves phase. Single phase Tb 1− x Pr x Fe 1.93B 0.15 with cubic MgCu 2-type structure forms up to x=0.3 as determined by X-ray diffraction. In the range of high Pr content, the boron atoms preferentially combine with rare-earth atoms to form the Nd 2Fe 14B-type phase. The results of lattice parameter and Curie temperature show that the Pr solubility limit for Tb 1− x Pr x Fe 1.93B 0.15 is reached in the range of x from 0.3 to 0.5. Large spontaneous magnetostriction of λ 111>2100 ppm is observed for the Laves phases in the Tb 1− x Pr x Fe 1.93B 0.15 alloys with 0⩽ x⩽0.3. Linear magnetostriction at room temperature of the single phase Tb 1− x Pr x Fe 1.93B 0.15 alloys decreases with increasing Pr content.

Magnetization processes and magnetostriction of Tb0.27Dy0.73Fe2 single crystal along 〈110〉 direction

The magnetostriction and magnetization process of a twin-free Tb0.27Dy0.73Fe2 single crystal along the 〈110〉 direction has been studied by strain gauge, vibrating sample magnetometer, and domain observation techniques. It was observed that the magnetostriction of the sample remained unchanged with increasing magnetic fields when H<1 kOe and quickly increased in the range 1<H<7.5 kOe. No “jump” effect was observed during the magnetization process and the magnetostrictive hysteresis was large when H<2.5 kOe. Observations by the Bitter colloid technique at room temperature revealed curved domain walls which became straight at higher and lower temperatures in {100} and {111}, respectively, indicating the transition to different 180° walls for H<1 kOe. The domain patterns were clearest on a {100} surface. Above the spin reorientation temperature, 109° and 71° wall motions dominated the magnetization process in the range 1.5 kOe<H<4 kOe, but below it, clear 90° wall motions were observed. Little change in the magnetized domain pattern was observed at different temperatures suggesting that many domain walls occupy the same planes. Similar room temperature patterns were observed at remanence with an applied stress along 〈111〉 in excess of 5 MPa. These results are consistent with theoretical magnetomechanical behavior based on a 〈1uu〉, 0<u<1, transition in easy direction.

High Noise Resistance of Fe–45 at.%Pd Alloy Film with High Magnetostrictive Susceptibility

The Fe–45 at.%Pd alloy film with high electromagnetic noise resistance and high magnetostrictive susceptibility was developed. In addition, the practical purpose was to propose a new method for accurately evaluating the magnetostrictive susceptibility at different applied magnetic fields. The magnetostrictive susceptibility obtained by the Fe–45 at.%Pd alloy film makes it an appropriate remote actuator in low magnetic fields below 300 Oe. The maximum magnetostrictive susceptibility was 2.9 ppm/Oe at 78 Oe. The magnetostrictive susceptibility of the Fe–45 at.%Pd alloy film was higher than that of a giant magnetostrictive Tb0.3Dy0.7Fe2 alloy film from 25 to 250 Oe.

Formation of δ phase and its effects on magnetic properties and magnetostriction of Tb 0.5Pr 0.5(Fe 0.4+ xCo 0.6− x) 1.9 (0⩽ x⩽0.6)

Structure, magnetic properties and magnetostriction of Tb 0.5Pr 0.5(Fe 0.4+ x Co 0.6− x ) 1.9 (0⩽ x⩽0.6) alloys are investigated. The existence of the δ phase for 50% Tb and 50% Pr is beneficial to the formation of the MgCu 2-type Laves phase. The composition dependence of Curie temperature has the same trend as the Slater–Pauling curve for the moment of Fe–Co alloys. The saturation magnetization M s and the remanence M R decrease, whereas the coercivity i H c increases with decreasing Co content, due to the increased amount of the non-cubic PuNi 3-type phase. The polycrystalline magnetostriction | λ ∥− λ| of the alloys at room temperature increases with increasing magnetic field and does not achieve saturation up to 796 kA/m.

Formula omitted] Directional growth of polycrystalline magnetostrictive Tb xDy 1− xFe y compounds by casting in a strong unidirectional gradient

Rods of highly magnetostrictive polycrystalline Tb x Dy 1− x Fe y materials are elaborated by casting in a cylindrical mould with cooling imposed from the bottom which leads to a fast vertical unidirectional growth. A 〈1 1 0〉 orientation is obtained along the axis of the rods parallel to the growth direction. The magnetostrictive properties are remarkable along the rods axis comparable to those of 〈1 1 1〉 rods. The saturated magnetostriction measured in a parallel magnetic field is λ ‖ =1124×10 −6 under 0 MPa and increases to 1760×10 −6 under a compressive stress of 25 MPa. The pseudolinear variation of the magnetostriction with the internal magnetic field Δλ ‖/μ 0 ΔH int reaches 640×10 −6/0.04 T under 9.9 MPa. The texture and the good magnetostrictive properties are reproducible.

Effects of high temperature annealing on the chemical homogeneity and Magnetostriction of Tb0.3Dy0.7Fe1.90 Intermetallic Compound

A rare earth-iron intermetallic compound Tb0.3Dy0.7Fe1.90, also called Terfenol-D, has a gigantic room temperature magnetostriction at a relatively small magnetic field. In this study microsegregation of Tb and Dy in directionally solidified Terfenol-D was investigated. It was predicted from a calculated phase diagram and experimentally verified that Tb concentration at the center of the cell which solidified earlier was lower than that at the cell boundary. In order to homogenize this microsegregation, specimens were annealed at 1000°C for 40 hours, and various magnetic properties were measured as a function of applied field under uniaxial compressive stress in the range from 0.5 to 1.2 MPa. After the annealing, the maximum magnetostriction increased at a compressive stress below 9 MPa, magnetostrictive coefficient d33 and magneto-elastic coupling coefficient k33 increased, but permeability decreased. These results may be due to the reduction of magnetocrystalline energy which was locally very high before annealing due to microsegregation.

Effect of the pulverization processes on the magnetostrictive characteristics on giant magnetostrictive Tb0.3Dy0.7Fe2 thin film

Effect of the pulverization processes on the magnetostrictive characteristics on giant magnetostrictive Tb0.3Dy0.7Fe2 thin film