Magnetostrictive Tb Research Articles

Magnetoelectric voltage gain effect in a long-type magnetostrictive/piezoelectric heterostructure

We report a large voltage gain of 130, together with a high magnetoelectric voltage coefficient of 7.6 V/Oe, in a long-type heterostructure made by combining a coil-wound, length-magnetized magnetostrictive Tb0.3Dy0.7Fe1.92 (Terfenol-D) alloy plate and a length-polarized piezoelectric 0.7Pb(Mg1/3Nb2/3)O3–0.3PbTiO3 single-crystal plate along the length direction. The observed voltage gain is found to originate from the product effect of the electromagnetic induction in the coil and the resonance magnetoelectric effect in the heterostructure.

The influence of nanoparticle size on the magnetostrictive properties of cluster-assembled Tb–Fe nanofilms

The giant magnetostrictive Tb–Fe films assembled by nanoparticles have been prepared by the low energy cluster beam deposition. The dependence of the magnetostriction on the size of the nanoparticles is examined for the films. It is shown that the nanofilms have obtained higher saturation magnetostriction at the cluster size of 30 nm in average. The dependence of magnetostriction on particle size is ascribed to the degree of magnetic anisotropy which is related to the effective distance of exchange coupling between the adjacent Tb–Fe nanoparticles. This work demonstrates that the magnetostriction can be varied by tuning the particle size, which is important for control over the magnetostrictive properties of the films at nanoscale.

Resonance converse magnetoelectric effect in a dual-mode bilayered composite of Pb(Mg 1/3Nb 2/3)O 3–PbTiO 3 and Tb 0.3Dy 0.7Fe 1.92

We report the resonance converse magnetoelectric (CME) effect in a bilayered composite with two different resonance modes. The composite consists of a thickness-polarized piezoelectric 0.7Pb(Mg 1/3Nb 2/3)O 3–0.3PbTiO 3 (PMN–PT) crystal plate and a length-magnetized magnetostrictive Tb 0.3Dy 0.7Fe 1.92 (Terfenol-D) alloy plate. A low-frequency bending mode resonance is observed in the composite in addition to a high-frequency longitudinal mode resonance. The bending and longitudinal mode resonances are found at 17.5 and 66.5 kHz, respectively, while their respective resonance CME coefficients are as large as 4.1 and 7.9 G/V, at an optimal bias magnetic field of 400 Oe. This dual-mode resonance CME effect forms a basis for dual-mode/-frequency operations of coil-free electromagnetic devices.

Passivity of Tb0·3Dy0·7Fe1·92 in alkaline solution and its breakdown by chloride ions

The passivation and pitting corrosion behaviour of stoichiometric Laves phase magnetostrictive compound Tb0·3Dy0·7Fe1·92, was investigated in 0·02M NaOH solution at different chloride ion concentrations (0·001–0·1M) by cyclic potentiodynamic polarisation. A systematic decrease in breakdown potential and corresponding increase in anodic current densities was observed with increasing chloride concentration. Potentiostatic currents were measured at several applied potentials in the passive range. The incubation period of pitting decreased with increasing chloride concentration. Microscopic examination of corroded surfaces after cyclic polarisation scans revealed that the attack by chloride ions was localised along arrays of active rare earth rich phase. At higher chloride levels, these phases were undermined. The number of pits and pit size increased with increasing chloride concentration. Electrochemical impedance spectroscopy conducted at open circuit potential and 50 mV above breakdown potential confirmed increasing corrosion rate with increasing chloride concentration. It has been concluded that the significant mechanistic step in the pitting corrosion of Tb0·3Dy0·7Fe1·92 is adsorption of metal–chloride complex species.

STRUCTURE AND MAGNETIC PROPERTIES OF TB0.27 DY0.73FE1.9+xTI0.05 COMPOUNDS

Structure, Curie temperature, and magnetostriction have been systemically investigated for Tb 0.27 Dy 0.73 Fe 1.9+x Ti 0.05 compounds using X-ray diffraction, vibrating sample magnetometer, and standard strain gauge technique. The samples show pure MgCu 2-type Laves phase when x≥0.2, and a small amount of second phases appear when x>0.2. The lattice parameters and the Curie temperatures change modestly with increasing Fe content. The magnetostriction of Tb 0.27 Dy 0.73 Fe 1.9+x Ti 0.05 compounds shows strong dependence on Fe content.

Structure and magnetostriction of Tb 0.2Pr 0.8(Fe 0.4Co 0.6) 1.93−xC x intermetallic compounds

The structure and magnetostriction of Tb 0.2Pr 0.8(Fe 0.4Co 0.6) 1.93− x C x intermetallic compounds were studied by X-ray diffraction and magnetic measurements. Almost a single cubic Laves phase forms in the alloys for x ≤0.20, and a small amount of C can inhibit the formation of the 1:3 phase. The lattice parameter increases when 0≤ x≤0.15, while the T c and the spontaneous magnetization decreases with increasing x. The lattice parameter decreases slowly when 0.15≤ x≤0.30, while the T c decreases evidently with increasing x. The magnetostriction λ a (= λ ∥– λ ⊥) is improved at low magnetic fields at room temperature for the compounds with 0.05≤ x≤0.10, indicating that these C-containing compounds are promising magnetostrictive materials.

Dual-mode magnetoelectric effect in laminate composite of Terfenol-D alloy and PMN–PT transformer with double output ports

The magnetoelectric effect of a laminate composite made by sandwiching a Rosen-type Pb(Mg1/3Nb2/3)O3–PbTiO3 (PMN–PT) single crystal transformer between two length-magnetized magnetostrictive Tb0.3Dy0.7Fe1.92 (Terfenol-D) alloy plates has been investigated. An additional giant sharp longitudinal–longitudinal (L–L) mode resonant magnetoelectric voltage coefficient of 15.6 V Oe−1 due to the transformer voltage gain effect was observed besides the longitudinal–transverse (L–T) mode magnetoelectric voltage coefficient of 4.0 V Oe−1. Moreover, our novel dual-mode (L–L and L–T) laminate can provide two independent output ports, which makes the composite a promising material for multifunctional application in magnetic sensors and magnetoelectric transducers.

Effects of Ti addition on the microstructure and magnetic properties of magnetostrictive Tb–Dy–Fe alloys

Alloys of Tb 0.3 Dy 0.7 Fe 1.95− x Ti x were vacuum induction melted and investigated for microstructural features and magnetic properties . Ti addition aids in diminishing the formation of pro-peritectic (Dy, Tb)Fe 3 phase at the expense of TiFe 2 phase formation. The magnetostriction was found to improve with the addition of Ti. Ti addition was also found to influence the saturation magnetization , Fe magnetic moment and Curie temperature of (Tb, Dy)Fe 2 phase.

Synthesis of High‐performance Magnetostrictive Tb0.3Dy0.7Fe2 by Unidirectional Solidification in Microgravity

Giant magnetostrictive materials, Tb(0.297)Dy(0.679)Fe(2), were synthesized by unidirectional solidification of a mixture of Tb(0.99)Fe(2) and Dy(0.97)Fe(2) alloys in microgravity with magnetic field of 0-0.12 T. Tb(0.297)Dy(0.679)Fe(2) is a mixed crystal of TbFe(2) and DyFe(2). Tb(0.297)Dy(0.679)Fe(2) synthesized in microgravity with no magnetic field had sheet dendrites structure with 300 (cooling direction) x 200 x 30 microm (thickness) and Fe-rich layer between the sheet dendrites, and they exhibited a tendency for crystalline orientation of <110> and <111> with the cooling direction. The magnetostriction with the cooling direction was 9000 ppm at an external magnetic field of 120 mT. In contrast, Tb(0.297)Dy(0.679)Fe(2) synthesized by unidirectional solidification in normal gravity with no magnetic field had a dendrite structure with a 30-mum diameter x 250-microm length growing in the cooling direction and no preferred orientation. The magnetostriction along the cooling direction was 2000 ppm at an external magnetic field of 120 mT. Analysis of the solidification in microgravity with magnetic field revealed that the dendrites oriented along the cooling direction and that the tendency for crystalline orientation of <110> and <111> with the cooling direction increased with magnetic field. Examination of the solidification in normal gravity with magnetic field indicated that Tb(0.297)Dy(0.679)Fe(2) consisted of sheet dendrites without orientation and revealed no preferred orientation. The magnetostriction along the cooling direction increased with increases in the magnetic field. The effects of microgravity and magnetic field on the structure and crystalline orientation were considered.

Synthesis and magnetostriction of TbxPr1−x(Fe0.8Co0.2)1.9 cubic Laves alloys

Polycrystalline magnetostrictive alloys TbxPr1−x(Fe0.8Co0.2)1.9 (0≤x≤0.4) which cannot be obtained under normal pressure were synthesized by high-pressure annealing. Measurements of crystal structure, Curie temperature, magnetization, and magnetostriction were made on TbxPr1−x(Fe0.8Co0.2)1.9 alloys. X-ray diffraction results show that the alloys exhibit C15 cubic Laves phase with MgCu2-type structure. The lattice parameter decreases with increasing Tb concentration, while the Curie temperature increases. Because of the antiparallel magnetic moment of Tb and Pr, the saturation magnetization decreases with increasing Tb concentration. The magnetostriction of Tb0.05Pr0.95(Fe0.8Co0.2)1.9 shows a peak at low magnetic fields, while that of Tb0.4Pr0.6(Fe0.8Co0.2)1.9 exhibits a minimum in the whole range of magnetic fields.

Magnetomechanical properties of epoxy-bonded (Tb0.3Dy0.7)1−xPrxFe1.55 (0 ⩽ x ⩽ 0.4) pseudo-1–3 magnetostrictive composites

Pseudo-1–3 magnetostrictive composites consisting of stabilizer (B, Co)-free, light rare earth (Pr)-containing magnetostrictive (Tb0.3Dy0.7)1−xPrxFe1.55 (0 ⩽ x ⩽ 0.4) particles with a size distribution of 10–300 µm embedded and aligned in a passive epoxy matrix using 0.5 volume fraction are fabricated. The quasistatic magnetomechanical properties of the composites are investigated and compared with their monolithic (Tb0.3Dy0.7)1−xPrxFe1.55 alloys, as a function of the Pr content x. The composites show similar qualitative trends in properties with the alloys for all x. The (Tb0.3Dy0.7)0.75Pr0.25Fe1.55 composite and alloy exhibit the smallest coercivity Hc, the largest magnetostriction λ and the highest piezomagnetic coefficient d33 due to the successful compensation for magnetocrystalline anisotropy. The (Tb0.3Dy0.7)0.75Pr0.25Fe1.55 composite demonstrates a large saturation magnetostriction λs of 793 ppm at 700 kA m−1 and a high d33 of 3.2 nm A−1 at 140 kA m−1. These values approach 81% and 85% of its alloy values at the same field levels. The good properties make the (Tb0.3Dy0.7)0.75Pr0.25Fe1.55 composite and alloy a promising magnetostrictive material system.

Giant magnetoelectric effect in mechanically clamped heterostructures of magnetostrictive alloy and piezoelectric crystal-alloy cymbal

We experimentally and theoretically report a giant magnetoelectric (ME) effect in a heterostructure made by clamping a bar-shaped magnetostrictive Tb0.3Dy0.7Fe1.92 (Terfenol-D) alloy actuator and a cymbal-type piezoelectric 0.7Pb(Mg1/3Nb2/3)O3–0.3PbTiO3(PMN–PT) (PMN-PT) single crystal-brass alloy transducer in a brass alloy frame. The reported ME effect originates from the stress-mediated product of the magnetostrictive effect in the Terfenol-D bar actuator and the mechanically transformed/amplified piezoelectric effect in the PMN PT-brass cymbal transducer under mechanically clamped conditions. The heterostructure exhibits a giant ME voltage coefficient (αV) of 440mV∕Oe at an optimal magnetic bias field of 400Oe besides showing good linearity between the induced ME voltage and the applied ac magnetic field in the field range of 10−3–10Oe. This αV is larger than that of conventional Terfenol-D/PMN-PT laminated composites.

Calibration and characterisation with a new laser-based magnetostriction measurement system

Abstract A laser-based magnet measurement system has been developed to measure the magnetostrictive strain of large cylindrical samples. The measurement system incorporates a solenoid capable of generating a maximum magnetic field intensity of 3000 Oe and a laser displacement sensor. For calibration and evaluation purposes, the positive magnetostrictions of two different types of giant magnetostrictive Tb–Dy–Fe-based materials were accessed with this system. A magnetostrictive strain of 622 ppm was obtained at 3000 Oe for Tb x Dy 1− x Fe 2− y , compared with 725 ppm for Tb 0.27 Dy 0.73 Fe 2 . A rod of sintered cobalt ferrite was also measured. This exhibited negative magnetostriction, with a maximum contraction of 260 ppm at 3000 Oe.

Magnetostriction and hysteresis of ⟨1 1 0⟩ oriented Tb0.29Dy0.48Ho0.23Fe2 single crystal

Magnetostriction behaviour and magnetostriction hysteresis of the single crystal alloy Tb0.29Dy0.48Ho0.23Fe2 are investigated experimentally and theoretically. The oriented ⟨1 1 0⟩ single crystals of the magnetostrictive alloy Tb0.29Dy0.48Ho0.23Fe2 are successfully prepared by the optical floating zone melting method. The single crystals are characterized by optical metallography, x-ray diffraction and x-ray Laue back-reflection measurement. The giant magnetostrictive properties are achieved in a wide operating temperature range from −60 to 80 °C. The calculated magnetostriction of the present alloy is reduced by only 6%, but the magnetostriction hysteresis (Wh) is reduced by more than 30%, compared with the traditional Terfenol-D giant magnetostrictive alloy. The magnetostriction behaviour is modelled using phenomenological theory. The rotation paths of magnetic domain moments are mathematically calculated and hence the resultant magnetostriction is obtained. The theoretical model of magnetostriction hysteresis Wh is proposed and the intrinsic factors of Wh are determined, which can well explain the pre-stress and temperature dependence of magnetostriction hysteresis.

Enhanced magnetoelectric effect in longitudinal-transverse mode Terfenol-D∕Pb(Mg1∕3Nb2∕3)O3–PbTiO3 laminate composites with optimal crystal cut

Magnetoelectric (ME) laminate composite consisting of optimal crystal cut thickness-polarized piezoelectric 0.7Pb(Mg1∕3Nb2∕3)O3–0.3PbTiO3 (PMN-PT) single crystal and the length-magnetized magnetostrictive Tb0.3Dy0.7Fe1.92 (Terfenol-D) alloy has been fabricated. The cut optimization of PMN-PT crystal greatly enhances the longitudinally magnetized-transversely polarized (L-T) mode ME effect, which has a superior ME voltage coefficient αE of ∼3.02V∕cmOe in low frequency band. Near the resonance frequency of 95kHz, the coefficient dramatically increases and reaches the maximized value of 33.2V∕cmOe, which is almost two times larger than the previously reported ⟨001⟩-oriented PMN-PT crystal based L-T mode laminate composite.

An approach for the development of protective coatings for the novel magnetostrictive material Tb0.3Dy0.7Fe1.92

A logical approach towards the development of protective metallic coatings for the newly developed pseudo-binary rare earth magnetostrictive material Tb0.3Dy0.7Fe1.92 has been put forth. Based on the proposal, experimental trials were conducted on nickel-based coatings, produced by electrodeposition and electroless plating techniques. Direct current electrodeposition of nickel was conducted using both aqueous and non-aqueous plating baths. Non-aqueous electrodeposition produced adherent nickel deposits unlike aqueous electrodeposition and electroless plating methods. The main cause of poor coating adherence in aqueous electrodeposition and electroless plating has been identified as excessive hydrogen evolution. The physical disintegration of the substrate due to hydrogen embrittlement has been briefly addressed.

Structure and magnetic properties of melt-spun Tb 0.27Dy 0.73Fe x ribbons

The structure and magnetic properties of the melt-spun ribbons of Tb 0.27Dy 0.73Fe x alloy are investigated as a function of various wheel speeds during melt-quenching using a single-roll technique. It is found that Tb 0.27Dy 0.73Fe x alloy is difficult to be fabricated as amorphous state by using the melt-quenching method. X-ray diffractions show that all these ribbons for x=1.7−2.0 are the MgCu 2-type phase at the wheel speed of 45 m s −1. For Tb 0.27Dy 0.73Fe x alloy, the high wheel speed is beneficial to eliminate the RFe 3 phase and form the perfect MgCu 2-type phase. Compared with the bulk of Tb 0.27Dy 0.73Fe 1.95, these ribbons exhibit higher intrinsic coercivity value and their saturation magnetizations increase as well. The magnetostriction of Tb 0.27Dy 0.73Fe 1.95 composite with 4% epoxy resin is 640×10 −6 at 900 kA m −1.

Magnetostriction of Tb0.1Ho0.9−xPrx(Fe0.9B0.1)2 (x=–0.4) compounds

The structural and magnetic properties of Tb0.1Ho0.9−xPrx(Fe0.9B0.1)2 (x=0, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, and 0.4) compounds are investigated. The compounds with 0⩽x⩽0.25 are found to stabilize in single cubic Laves phase structures. Small quantities of the (Tb,Ho,Pr)2Fe14B phase and rare-earth phases for x⩾0.3 and also the (Tb,Ho,Pr)(Fe,B)3 phase for x⩾0.35 are observed along with the Laves phase. The saturation magnetization and Curie temperature are found to decrease with Pr content. However, the magnetostriction (at 10kOe) is found to increase with Pr content. The x=0.15 compound is found to exhibit a possible anisotropy compensation between the (Tb∕Ho) and Pr sublattices. The easy magnetization direction (EMD) is found to rotate toward ⟨113⟩ as the Pr content increases, up to x=0.25, and for x⩾0.35 there is a tendency for the EMD to shift toward ⟨111⟩.

Development of a magetnetostrictive transducer for nondestructive testing of concrete structures

A magnetostrictive transducer operating at 100kHz using rare earth transition metal giant magnetostrictive material for nondestructive testing (NDT) applications was designed and fabricated. The giant magnetostrictive Tb0.3Dy0.7Fe2 material was chosen as the active element for the present purpose. From the impedance measurements, the resonant frequency of the transducer is found to be 100kHz. The performance of the transducer was validated by carrying out NDT on a test concrete block with delaminated regions, using the ultrasonic through-transmission technique and the pitch-catch method.

PMN-PT single crystal and Terfenol-D alloy magnetoelectric laminated composites for electromagnetic device applications

Magnetoelectric laminated composites of a length-magnetized magnetostrictive Tb0.3Dy0.7Fe1.92 (Terfenol-D) alloy plate sandwiched between two thickness-polarized, electro-parallel-connected piezoelectric 0.7Pb (Mg1/3Nb2/3)O3-0.3PbTiO3 (PMN-PT) single crystal plates were fabricated and their converse magnetoelectric properties were evaluated. An electromagnetic control device using a laminated composite as the control element and an Alnico biasing magnet, two Mn-Zn F-yokes and a Mu-metal movable plate as the magnetic circuit was developed and characterized. The distribution of the dc magnetic flux lines and magnetic inductions of the device were analyzed using a finite element method. The quasistatic and dynamic magnetic inductions of the device were measured, together with the generative forces. The results revealed that the device has linear voltage-controlled magnetic inductions in excess of 0.6 G/V with flat responses in the measured frequency range of 0.1-40 kHz and large generative forces over 0.7 N at 160 V at the designated gaps of 1.0-1.2 mm. This coil-free device could be useful in broadband and precision magnetic flux/force control applications with negligible Joule heating losses.