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Torsion and magnetic field measurements using inverse Wiedemann effect in glass-covered amorphous wires
Sensors and Actuators 85 Ž2000. 217–220 www.elsevier.nlrlocatersna
Torsion and magnetic field measurements using inverse Wiedemann effect in glass-covered amorphous wires H. Chiriac a , E. Hristoforou b, Maria Neagu a,) , I. Darie a , Cornelia Hison a a
National Institute of Research and DeÕelopment for Technical Physics, 47 Mangeron BouleÕard, 6600 Iasi 3, Romania b Metrology Laboratory, Technological and Educational Institution of Chalkis, Psahna, Euboea 34400 Greece Received 24 September 1999; received in revised form 18 January 2000; accepted 24 January 2000
Abstract This paper presents results concerning inverse Wiedemann effect ŽIWE. dependence on the torsion and d.c. magnetic field applied along the length of the Fe 77.5 Si 7.5 B15 glass-covered amorphous wires tested in the as-cast state both before and after glass removal. In the absence of torsion during measurements, the IWE voltage is zero. Increasing the torsion value up to about 55 radrm increases the value of the induced voltage until it reaches a maximum. In the 0.02–0.03 mT range there is a linear dependence of the IWE voltage on the d.c. magnetic field. The obtained results suggest the possibility of using Fe 77.5 Si 7.5 B15 glass-covered amorphous wires as sensing elements for torsion and magnetic field, based on the IWE. q 2000 Elsevier Science S.A. All rights reserved. Keywords: Glass-covered amorphous wires; Inverse Wiedemann effect; Magnetic anisotropy; Magnetic field sensor; Torsion sensor
1. Introduction The application of AconventionalB amorphous magnetic wires with diameters up to about 130 mm obtained by the in-rotating-water spinning method are specially based on their bistable behaviour resulting from the large Barkhausen effect ŽLBE. as well as on other effects like Matteucci and inverse Wiedemann effect ŽIWE. w1–5x. The glass-covered amorphous wires have been extensively studied recently, and they were found to be suitable for applications that replace the conventional amorphous wires or in other new ones, giving the possibility to miniaturise the sensor elements and ensuring a high corrosion and mechanical resistance. Glass covered amorphous wires consist of a cylindrical metallic core with typical diameters of 3 to 27 mm covered by a glass insulation with typical thickness of 2 to 15 mm, such wires being obtained directly from the melt by the glass-coated melt spinning method. The magnetic behavior of the glass-covered amorphous wires is typically characterized by a rectangular hysteresis loop due to the large Barkhausen effect that occurs at relatively low values of the axial magnetic field w5–8x. The LBE consists in an abrupt magnetization rever)
Corresponding author. Tel.: q40-32-130680; fax: q40-32-231132. E-mail address: [email protected] ŽM. Neagu..
sal in the axially magnetized cylindrical inner core at a well-defined value of the axial field, called the switching field. The IWE consists in the appearance of the longitudinal component of magnetization in a twisted wire subjected to a circular field produced by an a.c. current flowing through it. In this paper, results concerning torsion and magnetic field dependence of the IWE voltage for Fe 77.5 Si 7.5 B15 glass-covered amorphous wire, with and without glass cover, are presented.
2. Experimental details and results We tested Fe 77.5 Si 7.5 B 15 glass-covered amorphous wires having the same metallic diameter Ž27 mm. and different thicknesses of the glass cover Ž5–15 mm.. The amorphous state of the wires was checked by specific measurements such as X-ray diffraction and differential thermal analysis. The amorphous wires were tested in the as-cast state both before and after glass removal. The glass removal was achieved by chemical etching with a hydrofluoric acid solution whose concentration was gradually diminished to avoid etching of the metal. Fig. 1 presents the schematic diagram of the experimental set-up used for IWE measurements. This set-up allows
0924-4247r00r$ - see front matter q 2000 Elsevier Science S.A. All rights reserved. PII: S 0 9 2 4 - 4 2 4 7 Ž 0 0 . 0 0 3 9 5 - 2
218
H. Chiriac et al.r Sensors and Actuators 85 (2000) 217–220
Fig. 1. Experimental set-up used for IWE measurements: Ž1. glass covered amorphous wire; Ž2. ceramic tube; Ž3, 4. electrical contacts; Ž5. pick-up coil; Ž6, 7. Helmholtz coils; Ž8, 9. torsion device; Ž10. frequency generator; Ž11. power amplifier; Ž12. d.c. generator; Ž13. a.c. amplifier; Ž14. voltage detector; Ž15. filter.
simultaneous application of the a.c. current through the wire and the torsion, as well as detection of the IWE voltage by a pick-up coil Ž5.. The external d.c. magnetic field was applied using Helmholtz coils Ž6, 7.. During the experiments, the a.c. current intensity and frequency were varied between 20 and 60 mA and 50 and 5000 Hz, respectively.
Fig. 3. The dependence of the second harmonic of the IWE voltage on the d.c. magnetic field for Fe 77.5 Si 7.5 B15 glass covered amorphous wires tested in the as-cast state, before Ža. and after Žb. glass removal.
Fig. 2 shows the dependence of the IWE voltage on the applied torsion for as-cast Fe 77.5 Si 7.5 B 15 glass-covered amorphous wires, having a metallic core of 27 mm diameter and 10-mm-thick glass cover, before ŽFig. 2a. and after ŽFig. 2b. glass removal. The values of the a.c. current frequency and a.c. magnetic field at the wire surface were 4 kHz and 60 Arm, respectively. Fig. 3 presents the dependence of the second harmonic of the IWE voltage, V 2 v , on the d.c. magnetic field for as-cast Fe 77.5 Si 7.5 B15 glass-covered amorphous wires having a metallic core of 27 mm diameter and 10-mm-thick glass cover, before ŽFig. 3a. and after ŽFig. 3b. glass removal. The intensity and frequency of the current flowing through the wire were 40 mA and 300 Hz, respectively. During the measurements 50 radrm torsion was applied along the length of the amorphous wire.
3. Disscusion
Fig. 2. The dependence of the IWE voltage on the applied torsion for Fe 77.5 Si 7.5 B15 glass covered amorphous wires tested in the as-cast state, before Ža. and after Žb. glass removal.
In glass-covered amorphous wires high internal stresses are induced during preparation. The coupling between these stresses and magnetostriction plays a significant role in the domain structure formation. In the case of positive magnetostrictive glass-covered amorphous wires ŽFe 77.5 Si 7.5 B 15 . this coupling leads, in a first approximation, to a domain structure consisting of an inner core
H. Chiriac et al.r Sensors and Actuators 85 (2000) 217–220
axially magnetized and an outer shell radially magnetized w5–8x. Helical magnetic anisotropy in amorphous wires can be induced by applying torsion during measurements or by thermal treatment of the sample in the presence of torsion w9–13x. In this case the magnetization rotates from the axial or radial direction in the inner core and outer shell, respectively, towards a helical direction; these magnetization changes have a different contribution to the magnitude of the IWE voltage. A magnetic field applied in a given direction to the amorphous wire produces a change in the magnetization along a transverse direction only when the magnetization has components initially oriented in the field direction and perpendicular to it. When the a.c. current orientation changes, the induced circular magnetic field is reversed and, for a critical value of this field, a switching of the magnetization occurs and a voltage in the pick-up coil is induced. This induced voltage presents a series of switching peaks, periodically spaced along the time axis. The a.c. magnetic field and magnetoelastic energy values increase with the distance to the wire axis: Hf Ž t . s Ž Io sin2 n tr2p R 2 . r
Ž 1.
Et Ž r . s Ž 3r2 . lmj r
Ž 2.
where Hf is the ac magnetic field; Et Ž r . is the magnetoelastic energy density; Io and n are the a.c. current intensity and frequency, respectively; R is the radius of the wire and r is the distance to the wire axis; l is the magnetostriction constant; m and j are the shear modulus and angular displacement per unit length, respectively. As follows from Fig. 2a and b, for Fe 77.5 Si 7.5 B 15 glasscovered amorphous wires tested in the as-cast state, in the absence of torsion during the measurements, the IWE voltage is zero both before and after glass removal. Increasing the torsion amplitude, the induced helical anisotropy increases for the as-cast amorphous wires before and after glass removal and the value of the induced voltage increases as well until it reaches the maximum. Further increase in torsion leads to a decrease of the induced voltage, approaching an approximately constant value for glass-covered wires, and becoming very small, compared to its maximum value, for wires after glass removal. Torsions up to about 55 radrm and 35 radrm could be detected using amorphous wires with and without glass cover, respectively. As can be seen in Fig. 3a and b, in the range 0.02–0.03 mT the IWE voltage depends linearly on the d.c. magnetic field applied along the amorphous wire. After glass removal, an increase of the IWE voltage is obtained, the slope of the response curve being similar to that obtained for glass-covered wires. The response sensitivity is about 5 VrmT. The experiments show that the response sensitivity is strongly dependent on the a.c. current frequency, in-
219
creasing up to about 10 VrmT when the frequency increases up to about 3 kHz.
4. Conclusions The dependence of the inverse Wiedemann effect in Fe 77.5 Si 7.5 B 15 glass-covered amorphous wires, with and without glass cover, on the torsion and d.c. magnetic field applied along the length of the wire was studied. Torsions up to about 55 radrm and 35 radrm can be detected using amorphous wires with and without glass cover, respectively. The IWE voltage depends linearly on the d.c. magnetic field in the range 0.02–0.03 mT. The obtained results suggest the possibility of using Fe-rich glass-covered amorphous wires as sensing elements for torsion and d.c. magnetic field. These sensing elements have small dimensions, high sensitivity and good mechanical and corrosion resistance.
References w1x P.T. Squire, D. Atkinson, M.R.J. Gibbs, S. Atalay, Amorphous wires and their applications, J. Magn. Magn. Mater. 132 Ž1994. 10–21. w2x H. Chiriac, E. Hristoforou, M. Neagu, I. Darie, T.A. Ovari, Amorphous wire delay lines used for magnetic field measurements, IEEE Trans. Magn. 33 Ž1997. 4041–4143. w3x E. Pulido, R.P. del Real, F. Conde, G. Rivero, M. Vazquez, E. Ascasibar, A. Hernado, Amorphous wire magnetic field and d.c. current sensor based on the Inverse Wiedeman Effect, IEEE Trans. Magn. 27, 6 Ž1991. 5241–5243. w4x S.N. Kane, G. Rivero, M. Vasquez, A. Hernando, in: L. Lanotte ŽEd.., Magnetoelastic Effects and Applications, Elsevier, Amsterdam, 1993, pp. 147–152. w5x M. Vazquez, A. Hernando, A soft magnetic wire for sensor applications, J. Phys. D: Appl. Phys. 29 Ž1996. 939–949. w6x H. Chiriac, T.A. Ovari, Amorphous glass-covered magnetic wires: preparation, properties, applications, Prog. Mater. Sci. 40 Ž5. Ž1996. 333–407. w7x H. Chiriac, C.S. Marinescu, M. Marinescu, New sensor based on FeSiB amorphous glass covered wire for torsion oscillations recording, J. Magn. Magn. Mater. Ž1999. in press. ´ ´ M. Neagu, Sensor applicaw8x H. Chiriac, C.S. Marinescu, T.-A. Ovari, tions of amorphous glass-covered wires, Sens. Actuators Ž1999. in press. w9x J. Gonzalez, N. Murillo, V. Larin, J.M. Barandiaran, M. Vazquez, A. Hernando, Magnetic bistability of glass-covered Fe-rich amorphous microwire: influence of heating treatments and applied tensile stress, Sens. Actuators, A 59 Ž1997. 97–100. w10x M. Vazquez, J. Gonzalez, J.M. Blanco, J.M. Barandiaran, G. Rivero, A. Hernando, Torsion dependence of the magnetization process in magnetostrictive amorphous wire, J. Magn. Magn. Mater. 96 Ž1991. 321–328. w11x J. Gonzalez, J.M. Blanco, J.M. Barandiaran, M. Vazquez, A. Hernando, G. Rivero, D. Niarchos, Helical magnetic anisotropy induced by current annealing under torsion in amorphous wires, IEEE Trans. Magn. 26 Ž5. Ž1990. 1798–1800. ´ ´ Gh. Pop, F. Barariu, Effect of glass removal w12x H. Chiriac, T.A. Ovari, on the magnetic behavior of FeSiB glass covered wires, IEEE Trans. Magn. 33 Ž1997. 782–787.
220
H. Chiriac et al.r Sensors and Actuators 85 (2000) 217–220
´ ´ C.S. Marinescu, V. Nagacevschi, Magnetic w13x H. Chiriac, T.A. Ovari, anisotropy in FeSiB glass covered wires, IEEE Trans. Magn. 32 Ž1996. 4755–4757.
Biographies Horia Chiriac received the BSc and PhD degrees in physics from the AAl.I CuzaB University of Iasi, Romania, in 1962 and 1978, respectively. Currently he is Director of the National Institute of Research & Development for Technical Physics, Iasi and associate professor in physics, of AAl.I CuzaB University of Iasi. His research topics are amorphous magnetic materials in the shape of ribbons, wires, glass-covered wires, thin solid films and sensors based on the abovementioned materials. EÕangelos Hristoforou received the DEng degree in electrical engineering from the University of Patras, Greece, in 1984 and the PhD degree in electronic and electrical engineering from King’s College, University of London. Currently he is head of Metrology Laboratory, TEI of Chalkis, Greece. His research topics are conceiving and developing electronic sensors based on magnetic materials. He has published more than 40 papers in journals, 20 papers in international conference proceedings and he owns six patents.
Maria Neagu received the BSc and PhD degrees in physics from the AAl.I CuzaB University of Iasi, Romania, in 1973 and 1995, respectively. Currently she is Head of the Department of Magnetic Materials and Devices at the National Institute of Research & Development for Technical Physics, Iasi. Her research topics are magnetostrictive materials and sensors based on these materials.
Iulian Darie received the BSc degree from the Electrotechnical Faculty AGh. AsachiB University of Iasi, Romania, in 1990. Currently he is working at the National Institute of Research and Development for Technical Physics, Iasi, Romania in the field of sensors and devices based on magnetic materials and is a PhD student in the same field.
Cornelia Hison received the DEng degree in technical physics from the Technical Physics Faculty , AAl. I. CuzaB University of Iasi, Romania, in 1995 and the master’s degree in Plasma and Spectroscopy from the same faculty in 1996. She is a PhD candidate of AAl. I. CuzaB University of Iasi. Currently she is scientific researcher at the National Institute of Research and Development for Technical Physics Iasi, Romania. Her research field of interest is soft magnetic nanocrystalline metallic ribbons and their applications.
Torsion and magnetic field measurements using inverse Wiedemann effect in glass-covered amorphous wires H. Chiriac a , E. Hristoforou b, Maria Neagu a,) , I. Darie a , Cornelia Hison a a
National Institute of Research and DeÕelopment for Technical Physics, 47 Mangeron BouleÕard, 6600 Iasi 3, Romania b Metrology Laboratory, Technological and Educational Institution of Chalkis, Psahna, Euboea 34400 Greece Received 24 September 1999; received in revised form 18 January 2000; accepted 24 January 2000
Abstract This paper presents results concerning inverse Wiedemann effect ŽIWE. dependence on the torsion and d.c. magnetic field applied along the length of the Fe 77.5 Si 7.5 B15 glass-covered amorphous wires tested in the as-cast state both before and after glass removal. In the absence of torsion during measurements, the IWE voltage is zero. Increasing the torsion value up to about 55 radrm increases the value of the induced voltage until it reaches a maximum. In the 0.02–0.03 mT range there is a linear dependence of the IWE voltage on the d.c. magnetic field. The obtained results suggest the possibility of using Fe 77.5 Si 7.5 B15 glass-covered amorphous wires as sensing elements for torsion and magnetic field, based on the IWE. q 2000 Elsevier Science S.A. All rights reserved. Keywords: Glass-covered amorphous wires; Inverse Wiedemann effect; Magnetic anisotropy; Magnetic field sensor; Torsion sensor
1. Introduction The application of AconventionalB amorphous magnetic wires with diameters up to about 130 mm obtained by the in-rotating-water spinning method are specially based on their bistable behaviour resulting from the large Barkhausen effect ŽLBE. as well as on other effects like Matteucci and inverse Wiedemann effect ŽIWE. w1–5x. The glass-covered amorphous wires have been extensively studied recently, and they were found to be suitable for applications that replace the conventional amorphous wires or in other new ones, giving the possibility to miniaturise the sensor elements and ensuring a high corrosion and mechanical resistance. Glass covered amorphous wires consist of a cylindrical metallic core with typical diameters of 3 to 27 mm covered by a glass insulation with typical thickness of 2 to 15 mm, such wires being obtained directly from the melt by the glass-coated melt spinning method. The magnetic behavior of the glass-covered amorphous wires is typically characterized by a rectangular hysteresis loop due to the large Barkhausen effect that occurs at relatively low values of the axial magnetic field w5–8x. The LBE consists in an abrupt magnetization rever)
Corresponding author. Tel.: q40-32-130680; fax: q40-32-231132. E-mail address: [email protected] ŽM. Neagu..
sal in the axially magnetized cylindrical inner core at a well-defined value of the axial field, called the switching field. The IWE consists in the appearance of the longitudinal component of magnetization in a twisted wire subjected to a circular field produced by an a.c. current flowing through it. In this paper, results concerning torsion and magnetic field dependence of the IWE voltage for Fe 77.5 Si 7.5 B15 glass-covered amorphous wire, with and without glass cover, are presented.
2. Experimental details and results We tested Fe 77.5 Si 7.5 B 15 glass-covered amorphous wires having the same metallic diameter Ž27 mm. and different thicknesses of the glass cover Ž5–15 mm.. The amorphous state of the wires was checked by specific measurements such as X-ray diffraction and differential thermal analysis. The amorphous wires were tested in the as-cast state both before and after glass removal. The glass removal was achieved by chemical etching with a hydrofluoric acid solution whose concentration was gradually diminished to avoid etching of the metal. Fig. 1 presents the schematic diagram of the experimental set-up used for IWE measurements. This set-up allows
0924-4247r00r$ - see front matter q 2000 Elsevier Science S.A. All rights reserved. PII: S 0 9 2 4 - 4 2 4 7 Ž 0 0 . 0 0 3 9 5 - 2
218
H. Chiriac et al.r Sensors and Actuators 85 (2000) 217–220
Fig. 1. Experimental set-up used for IWE measurements: Ž1. glass covered amorphous wire; Ž2. ceramic tube; Ž3, 4. electrical contacts; Ž5. pick-up coil; Ž6, 7. Helmholtz coils; Ž8, 9. torsion device; Ž10. frequency generator; Ž11. power amplifier; Ž12. d.c. generator; Ž13. a.c. amplifier; Ž14. voltage detector; Ž15. filter.
simultaneous application of the a.c. current through the wire and the torsion, as well as detection of the IWE voltage by a pick-up coil Ž5.. The external d.c. magnetic field was applied using Helmholtz coils Ž6, 7.. During the experiments, the a.c. current intensity and frequency were varied between 20 and 60 mA and 50 and 5000 Hz, respectively.
Fig. 3. The dependence of the second harmonic of the IWE voltage on the d.c. magnetic field for Fe 77.5 Si 7.5 B15 glass covered amorphous wires tested in the as-cast state, before Ža. and after Žb. glass removal.
Fig. 2 shows the dependence of the IWE voltage on the applied torsion for as-cast Fe 77.5 Si 7.5 B 15 glass-covered amorphous wires, having a metallic core of 27 mm diameter and 10-mm-thick glass cover, before ŽFig. 2a. and after ŽFig. 2b. glass removal. The values of the a.c. current frequency and a.c. magnetic field at the wire surface were 4 kHz and 60 Arm, respectively. Fig. 3 presents the dependence of the second harmonic of the IWE voltage, V 2 v , on the d.c. magnetic field for as-cast Fe 77.5 Si 7.5 B15 glass-covered amorphous wires having a metallic core of 27 mm diameter and 10-mm-thick glass cover, before ŽFig. 3a. and after ŽFig. 3b. glass removal. The intensity and frequency of the current flowing through the wire were 40 mA and 300 Hz, respectively. During the measurements 50 radrm torsion was applied along the length of the amorphous wire.
3. Disscusion
Fig. 2. The dependence of the IWE voltage on the applied torsion for Fe 77.5 Si 7.5 B15 glass covered amorphous wires tested in the as-cast state, before Ža. and after Žb. glass removal.
In glass-covered amorphous wires high internal stresses are induced during preparation. The coupling between these stresses and magnetostriction plays a significant role in the domain structure formation. In the case of positive magnetostrictive glass-covered amorphous wires ŽFe 77.5 Si 7.5 B 15 . this coupling leads, in a first approximation, to a domain structure consisting of an inner core
H. Chiriac et al.r Sensors and Actuators 85 (2000) 217–220
axially magnetized and an outer shell radially magnetized w5–8x. Helical magnetic anisotropy in amorphous wires can be induced by applying torsion during measurements or by thermal treatment of the sample in the presence of torsion w9–13x. In this case the magnetization rotates from the axial or radial direction in the inner core and outer shell, respectively, towards a helical direction; these magnetization changes have a different contribution to the magnitude of the IWE voltage. A magnetic field applied in a given direction to the amorphous wire produces a change in the magnetization along a transverse direction only when the magnetization has components initially oriented in the field direction and perpendicular to it. When the a.c. current orientation changes, the induced circular magnetic field is reversed and, for a critical value of this field, a switching of the magnetization occurs and a voltage in the pick-up coil is induced. This induced voltage presents a series of switching peaks, periodically spaced along the time axis. The a.c. magnetic field and magnetoelastic energy values increase with the distance to the wire axis: Hf Ž t . s Ž Io sin2 n tr2p R 2 . r
Ž 1.
Et Ž r . s Ž 3r2 . lmj r
Ž 2.
where Hf is the ac magnetic field; Et Ž r . is the magnetoelastic energy density; Io and n are the a.c. current intensity and frequency, respectively; R is the radius of the wire and r is the distance to the wire axis; l is the magnetostriction constant; m and j are the shear modulus and angular displacement per unit length, respectively. As follows from Fig. 2a and b, for Fe 77.5 Si 7.5 B 15 glasscovered amorphous wires tested in the as-cast state, in the absence of torsion during the measurements, the IWE voltage is zero both before and after glass removal. Increasing the torsion amplitude, the induced helical anisotropy increases for the as-cast amorphous wires before and after glass removal and the value of the induced voltage increases as well until it reaches the maximum. Further increase in torsion leads to a decrease of the induced voltage, approaching an approximately constant value for glass-covered wires, and becoming very small, compared to its maximum value, for wires after glass removal. Torsions up to about 55 radrm and 35 radrm could be detected using amorphous wires with and without glass cover, respectively. As can be seen in Fig. 3a and b, in the range 0.02–0.03 mT the IWE voltage depends linearly on the d.c. magnetic field applied along the amorphous wire. After glass removal, an increase of the IWE voltage is obtained, the slope of the response curve being similar to that obtained for glass-covered wires. The response sensitivity is about 5 VrmT. The experiments show that the response sensitivity is strongly dependent on the a.c. current frequency, in-
219
creasing up to about 10 VrmT when the frequency increases up to about 3 kHz.
4. Conclusions The dependence of the inverse Wiedemann effect in Fe 77.5 Si 7.5 B 15 glass-covered amorphous wires, with and without glass cover, on the torsion and d.c. magnetic field applied along the length of the wire was studied. Torsions up to about 55 radrm and 35 radrm can be detected using amorphous wires with and without glass cover, respectively. The IWE voltage depends linearly on the d.c. magnetic field in the range 0.02–0.03 mT. The obtained results suggest the possibility of using Fe-rich glass-covered amorphous wires as sensing elements for torsion and d.c. magnetic field. These sensing elements have small dimensions, high sensitivity and good mechanical and corrosion resistance.
References w1x P.T. Squire, D. Atkinson, M.R.J. Gibbs, S. Atalay, Amorphous wires and their applications, J. Magn. Magn. Mater. 132 Ž1994. 10–21. w2x H. Chiriac, E. Hristoforou, M. Neagu, I. Darie, T.A. Ovari, Amorphous wire delay lines used for magnetic field measurements, IEEE Trans. Magn. 33 Ž1997. 4041–4143. w3x E. Pulido, R.P. del Real, F. Conde, G. Rivero, M. Vazquez, E. Ascasibar, A. Hernado, Amorphous wire magnetic field and d.c. current sensor based on the Inverse Wiedeman Effect, IEEE Trans. Magn. 27, 6 Ž1991. 5241–5243. w4x S.N. Kane, G. Rivero, M. Vasquez, A. Hernando, in: L. Lanotte ŽEd.., Magnetoelastic Effects and Applications, Elsevier, Amsterdam, 1993, pp. 147–152. w5x M. Vazquez, A. Hernando, A soft magnetic wire for sensor applications, J. Phys. D: Appl. Phys. 29 Ž1996. 939–949. w6x H. Chiriac, T.A. Ovari, Amorphous glass-covered magnetic wires: preparation, properties, applications, Prog. Mater. Sci. 40 Ž5. Ž1996. 333–407. w7x H. Chiriac, C.S. Marinescu, M. Marinescu, New sensor based on FeSiB amorphous glass covered wire for torsion oscillations recording, J. Magn. Magn. Mater. Ž1999. in press. ´ ´ M. Neagu, Sensor applicaw8x H. Chiriac, C.S. Marinescu, T.-A. Ovari, tions of amorphous glass-covered wires, Sens. Actuators Ž1999. in press. w9x J. Gonzalez, N. Murillo, V. Larin, J.M. Barandiaran, M. Vazquez, A. Hernando, Magnetic bistability of glass-covered Fe-rich amorphous microwire: influence of heating treatments and applied tensile stress, Sens. Actuators, A 59 Ž1997. 97–100. w10x M. Vazquez, J. Gonzalez, J.M. Blanco, J.M. Barandiaran, G. Rivero, A. Hernando, Torsion dependence of the magnetization process in magnetostrictive amorphous wire, J. Magn. Magn. Mater. 96 Ž1991. 321–328. w11x J. Gonzalez, J.M. Blanco, J.M. Barandiaran, M. Vazquez, A. Hernando, G. Rivero, D. Niarchos, Helical magnetic anisotropy induced by current annealing under torsion in amorphous wires, IEEE Trans. Magn. 26 Ž5. Ž1990. 1798–1800. ´ ´ Gh. Pop, F. Barariu, Effect of glass removal w12x H. Chiriac, T.A. Ovari, on the magnetic behavior of FeSiB glass covered wires, IEEE Trans. Magn. 33 Ž1997. 782–787.
220
H. Chiriac et al.r Sensors and Actuators 85 (2000) 217–220
´ ´ C.S. Marinescu, V. Nagacevschi, Magnetic w13x H. Chiriac, T.A. Ovari, anisotropy in FeSiB glass covered wires, IEEE Trans. Magn. 32 Ž1996. 4755–4757.
Biographies Horia Chiriac received the BSc and PhD degrees in physics from the AAl.I CuzaB University of Iasi, Romania, in 1962 and 1978, respectively. Currently he is Director of the National Institute of Research & Development for Technical Physics, Iasi and associate professor in physics, of AAl.I CuzaB University of Iasi. His research topics are amorphous magnetic materials in the shape of ribbons, wires, glass-covered wires, thin solid films and sensors based on the abovementioned materials. EÕangelos Hristoforou received the DEng degree in electrical engineering from the University of Patras, Greece, in 1984 and the PhD degree in electronic and electrical engineering from King’s College, University of London. Currently he is head of Metrology Laboratory, TEI of Chalkis, Greece. His research topics are conceiving and developing electronic sensors based on magnetic materials. He has published more than 40 papers in journals, 20 papers in international conference proceedings and he owns six patents.
Maria Neagu received the BSc and PhD degrees in physics from the AAl.I CuzaB University of Iasi, Romania, in 1973 and 1995, respectively. Currently she is Head of the Department of Magnetic Materials and Devices at the National Institute of Research & Development for Technical Physics, Iasi. Her research topics are magnetostrictive materials and sensors based on these materials.
Iulian Darie received the BSc degree from the Electrotechnical Faculty AGh. AsachiB University of Iasi, Romania, in 1990. Currently he is working at the National Institute of Research and Development for Technical Physics, Iasi, Romania in the field of sensors and devices based on magnetic materials and is a PhD student in the same field.
Cornelia Hison received the DEng degree in technical physics from the Technical Physics Faculty , AAl. I. CuzaB University of Iasi, Romania, in 1995 and the master’s degree in Plasma and Spectroscopy from the same faculty in 1996. She is a PhD candidate of AAl. I. CuzaB University of Iasi. Currently she is scientific researcher at the National Institute of Research and Development for Technical Physics Iasi, Romania. Her research field of interest is soft magnetic nanocrystalline metallic ribbons and their applications.