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On the saturation magnetostriction in low magnetostrictive Co-rich amorphous wires
Sensors and Actuators 76 Ž1999. 372–375 www.elsevier.nlrlocatersna
On the saturation magnetostriction in low magnetostrictive Co-rich amorphous wires H. Chiriac a , Maria Neagu a
a,)
, E. Hristoforou
b
National Institute of Research and DeÕelopment for Technical Physics, 47 Mangeron BouleÕard, 6600 Iasi 3, Romania b Technological and Educational Institution of Chalkis, Psahna, Euboea 34400, Greece Accepted 22 October 1998
Abstract This paper presents some results concerning the saturation magnetostriction Ž ls . in low magnetostrictive Co-rich amorphous wires tested in the as-cast state and after annealing. The replacement of Co or Fe with small amounts of Cr and Ni in nearly zero magnetostrictive Co-rich alloys determines small positive or negative ls values, while the stress current annealing changes its magnitude. The saturation magnetostriction has been determined by means of the small-angle magnetisation rotation method and has been evaluated as q0.39 = 10y6 for Co 65.25 Fe 4.5 Si 12.25 B15 Cr2 Ni 1 and y1.15 = 10y6 for Co 68.15 Fe 2.35 Si 12.5 B15 Cr1 Ni 1 amorphous wires in the as-cast state. An increase up to about 5 times and a decrease up to about 2 times of ls was observed for Co 65.25 Fe 4.5 Si 12.25 B15 Cr2 Ni 1 and Co 68.15 Fe 2.35 Si 12.5 B15 Cr1 Ni 1 amorphous wire, respectively, after stress current annealing. q 1999 Elsevier Science S.A. All rights reserved. Keywords: Amorphous wires; Saturation magnetostriction; Stress current annealing
1. Introduction Magnetic amorphous wires obtained by in-rotating-water spinning method presents a special interest for basic research as well as for their potential applications. These materials are prospective for numerous types of sensors due to their wide range of possibilities to control the magnetic and magnetostrictive properties w1,2x. The saturation magnetostriction constant ls is the basic magnetoelastic quantity that determines the magnetic and magnetoelastic behaviour of the magnetostrictive materials. Control of the sign and value of ls by means of alloy composition and by annealing the samples is very important with the view of applications. This paper presents results concerning ls in the as-cast state as well as its dependence on the stress current annealing conditions in low magnetostrictive Co–Fe–Si– B– ŽCr,Ni. amorphous wires. We obtained amorphous wires having low positive or negative saturation magnetostriction by replacement of Co or Fe with small amounts of Cr and
) Corresponding author. Tel.: q40-32-130-680; Fax: q40-32-231-132; E-mail: [email protected]
Ni in nearly zero magnetostrictive Co-rich alloys. The saturation magnetostriction has been determined by means of the small angle magnetisation rotation method ŽSAMR. w3x.
2. Experimental details Amorphous wires with nominal compositions Co 65.25Fe 4.5 Si 12.25 B15 Cr2 Ni 1 and Co 68.15 Fe 2.35 Si 12.5 B15 Cr1 Ni 1 , 125 mm in diameter, were obtained by in-rotating-water spinning method. The small angle magnetisation rotation is determined by applying simultaneously a small amplitude ac magnetic field Ž Hac ., high dc magnetic field Ž Hdc . perpendicular and parallel to the axis of the wire and a tensile stress s . Hdc magnetic field must be high enough to produce the magnetisation saturation of the amorphous wire. The SAMR method is based on detection of the induced voltage V2f Žthe second harmonic of the applied ac magnetic field. in the receiving coil set around the amorphous wire. When a tensile stress s is applied on the wire Žat constant Hac and Hdc magnetic fields., V2f increases or decreases as a consequence of the increment of magnetoelastic anisotropy
0924-4247r99r$ - see front matter q 1999 Elsevier Science S.A. All rights reserved. PII: S 0 9 2 4 - 4 2 4 7 Ž 9 9 . 0 0 0 2 6 - 6
H. Chiriac et al.r Sensors and Actuators 76 (1999) 372–375
373
having a transverse or an axial easy axis, respectively. The change in V2f can be compensated by an adequate modification of Hdc , so that V2f takes the same value as before the stress was applied. The magnetostriction constant is obtained as:
ls s y Ž m 0 Msr3 . Ž D HdcrD s . , for V2 f and Hac s constant
Ž 1.
where m 0 Ms is saturation magnetization. The value of Hdc magnetic field for which SAMR method is suitable should be high enough for V2f Hdc2 to be constant w4x. The transverse magnetic field Hac was obtained by passing through the wire an electric current having 4 kHz frequency and the maximum value less than 50 Arm at the wire surface. The value of ac current was small enough to neglect the increase in temperature of the amorphous wire. The second harmonic V2f was detected using a lock-in amplifier.
3. Results and discussion Fig. 1 illustrates the DTA curves recorded for Co 65.25Fe 4.5 Si 12.25 B 15 Cr2 Ni 1 and Co 68.15 Fe 2.35 Si 12.5 B 15 Cr1 Ni 1 amorphous wires. The DTA measurements were made with a heating rate of 108Crmin. For Co 65.25 Fe 4.5Si 12.25 B15 Cr2 Ni 1 and Co 68.15 Fe 2.35 Si 12.5 B15 Cr1 Ni 1 amorphous wires, the Curie and crystallisation temperatures ŽTC and Tx . are: 513 K, 833 K and 533 K, 823 K, respectively. For Co-rich amorphous wires annealed up to about 20 Armm2 current density, the stabilised average temperature is up to about 450 K.
Fig. 2. The V2f dependence on the applied tensile stress s , with Hdc field as parameter, for amorphous wires tested in the as-cast state: Ža. Co 65.25 Fe 4.5 Si 12.25 B15 Cr2 Ni 1 and Žb. Co 68.15 Fe 2.35 Si 12.5 B 15 Cr1 Ni 1: v 700 Arm; ` 1600 Arm; ' 2400 Arm; ^ 3200 Arm.
Fig. 1. DTA curves for Co 65.25 Fe 4.5 Si 12.25 B15 Cr2 Ni 1 and Co 68.15Fe 2.35 Si 12.5 B15 Cr1 Ni 1 amorphous wires.
In order to establish the measurement conditions for ls determination, we analysed the dependence of the second harmonic V2f on the tensile stress s , Hac and Hdc magnetic fields. Fig. 2Ža. and Žb. shows the dependence of V2f on the applied stress s , with Hdc field as parameter, for Co 65.25Fe 4.5 Si 12.25 B 15 Cr2 Ni 1 and Co 68.15 Fe 2.35 Si 12.5 B 15 Cr1 Ni 1 amorphous wires, tested in the as-cast state. The V2f value decreases when Hdc increases. When s increases, V2f decreases for low positive Co 65.25 Fe 4.5 Si 12.25 B15 Cr2 Ni 1 and increases for low negative Co 68.15 Fe 2.35 Si 12.5 B15 Cr1 Ni 1 amorphous wires. The saturation magnetostriction ls has been evaluated as q0.39 = 10y6 for Co 65.25 Fe 4.5 Si 12.25 B15 Cr2 Ni 1 and y1.15 = 10y6 for Co 68.15 Fe 2.35 Si 12.5 B 15 Cr1 Ni 1 amorphous wires tested in the as-cast state. The measurements were made at 7 kArm of magnetic bias field for which V2f Hdc2 is constant. Having in mind to control the saturation magnetostriction value for these materials, we studied the influence of
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H. Chiriac et al.r Sensors and Actuators 76 (1999) 372–375
of the structural relaxation is important at low temperature. The maximum value of ls is obtained for annealing temperatures Tann ) Tc, which denotes that these changes are related to the creep-induced magnetic anisotropy that was observed in Co-rich amorphous wires w6x.
4. Conclusions Low positive or negative magnetostrictive amorphous wires were obtained by replacement of Co or Fe with small amounts of Cr and Ni in nearly zero magnetostrictive Co-rich alloys. For Co 65.25 Fe 4.5 Si 12.25 B 15 Cr2 Ni 1 and Co 68.15 Fe 2.35 Si 12.5 B15 Cr1 Ni 1 amorphous wires in the ascast state, the saturation magnetostriction ls has been evaluated as q0.39 = 10y6 and y1.15 = 10y6 , respectively. After stress current treatments at annealing temperatures Tann ) Tc , the saturation magnetostriction ls exhibits the following behaviour: increases about 5 times for Co 65.25 Fe 4.5 Si 12..25 B15 Cr2 Ni 1 amorphous wires; decreases about 2 times for Co 68.15 Fe 2.35 Si 12.5 B15 Cr1 Ni 1 amorphous wires. These materials are very attractive for a wide range of sensing applications especially for those based on the GMI effect and for security system sensors. The tailoring of magnetic and magnetostrictive properties for special applications can be also realised. Fig. 3. The dependence of saturation magnetostriction ls on the current density for 30 min of stress current annealing under 100 MPa, Ža. Co 65.25 Fe 4.5 Si 12.25 B15 Cr2 Ni 1 and Žb. Co 68.15 Fe 2.35 Si 12.5 B 15 Cr1 Ni 1.
stress current annealing on ls . The elevated temperatures were obtained by Joule heating produced by an electric current passing through the amorphous wire. The current density and annealing time were increased up to 40 Armm2 and 35 min, respectively. To evaluate the average temperature inside the samples during the annealing current flowing, the saturation magnetisation was measured as a function of the temperature during conventional furnace treatment and compared to that obtained by Joule heating w5x. Fig. 3Ža. and Žb. shows the changes in saturation magnetostriction for Co 65.25 Fe 4.5 Si 12.25 B 15 Cr 2 Ni 1 and Co 68.15 Fe 2.35 Si 12.5 B15 Cr1 Ni 1 amorphous wires, respectively tested after stress current annealing for 30 min, under 100 MPa tensile stress. For low positive magnetostrictive Co 65.25 Fe 4.5 Si 12.25B 15 Cr2 Ni 1 amorphous wires, ls value remains unchanged up to about 20 Armm2 and then strongly increases. A peak about 5 times higher than in the as-cast state was obtained for about 35 Armm2 . For low negative magnetostrictive Co 68.15 Fe 2.35 Si 12.5 B15 Cr1 Ni 1 amorphous wires, ls decreases about 2 times after stress current annealing. The obtained results can be analysed taking into account the structural relaxation and induced transverse magnetic anisotropy after stress current annealing. The effect
References w1x P.T. Squire, D. Atkinson, S. Atalay, Magnetostrictive and magnetoelastic properties of rapidly quenched wires, IEEE Trans. Magn. 31 Ž1995. 1239–1248. w2x M. Vazquez, A. Hernando, A soft magnetic wire for sensor applications, J. Phys. D: Appl. Phys. 29 Ž1996. 939–949. w3x K. Narita, J. Yamasaki, H. Fukunaga, Measurement of saturation magnetostriction of a thin amorphous ribbon by means of small-angle magnetization rotation, IEEE Trans. Magn. 16 Ž1980. 435–439. w4x A. Mitra, M. Vazquez, Measurement of the saturation magnetostriction constant of amorphous wire, J. Appl. Phys. 67 Ž1990. 4986–4988. w5x M. Knobel, P. Allia P, C. Gomez-Polo, H. Chiriac, M. Vazquez, Joule heating in amorphous metallic wires, J. Phys. D: Appl. Phys. 26 Ž1995. 2398–2403. w6x L. Kraus, M. Vasquez, A. Hernando, Creep-induced magnetic anisotropy in a Co-rich amorphous wire, J. Appl. Phys. 76 Ž1994. 5343– 5348. Horia Chiriac received the BS and PhD degrees in Physics from the ‘Al.I Cuza’ University of Iasi, Romania, in 1962 and 1978, respectively. Currently he is Director of the National Institute of Research and Development for Technical Physics, Iasi and Associate Professor in Physics, ‘Al.I Cuza’ 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 above mentioned materials. Maria Neagu received the BS and PhD degrees in Physics from the ‘Al.I Cuza’ 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 and Development for Technical Physics, Iasi. Her research topics are magnetostrictive materials and sensors based on these materials.
H. Chiriac et al.r Sensors and Actuators 76 (1999) 372–375 Evangelos Hristoforou received the D.Eng. Degree in Electrical Engineering from the Engineering Faculty, University of Patras, Patras, Greece in 1984 and the PhD degree in Electrical Engineering from King’s College London, University of London, UK, in 1991. Currently he is Head of the Metrology Laboratory, Faculty of Engineering Applications, Technological and Educational Institution of Chalkis, Euboea, Greece. His research topics are sensors and actuators based on magnetic materials.
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On the saturation magnetostriction in low magnetostrictive Co-rich amorphous wires H. Chiriac a , Maria Neagu a
a,)
, E. Hristoforou
b
National Institute of Research and DeÕelopment for Technical Physics, 47 Mangeron BouleÕard, 6600 Iasi 3, Romania b Technological and Educational Institution of Chalkis, Psahna, Euboea 34400, Greece Accepted 22 October 1998
Abstract This paper presents some results concerning the saturation magnetostriction Ž ls . in low magnetostrictive Co-rich amorphous wires tested in the as-cast state and after annealing. The replacement of Co or Fe with small amounts of Cr and Ni in nearly zero magnetostrictive Co-rich alloys determines small positive or negative ls values, while the stress current annealing changes its magnitude. The saturation magnetostriction has been determined by means of the small-angle magnetisation rotation method and has been evaluated as q0.39 = 10y6 for Co 65.25 Fe 4.5 Si 12.25 B15 Cr2 Ni 1 and y1.15 = 10y6 for Co 68.15 Fe 2.35 Si 12.5 B15 Cr1 Ni 1 amorphous wires in the as-cast state. An increase up to about 5 times and a decrease up to about 2 times of ls was observed for Co 65.25 Fe 4.5 Si 12.25 B15 Cr2 Ni 1 and Co 68.15 Fe 2.35 Si 12.5 B15 Cr1 Ni 1 amorphous wire, respectively, after stress current annealing. q 1999 Elsevier Science S.A. All rights reserved. Keywords: Amorphous wires; Saturation magnetostriction; Stress current annealing
1. Introduction Magnetic amorphous wires obtained by in-rotating-water spinning method presents a special interest for basic research as well as for their potential applications. These materials are prospective for numerous types of sensors due to their wide range of possibilities to control the magnetic and magnetostrictive properties w1,2x. The saturation magnetostriction constant ls is the basic magnetoelastic quantity that determines the magnetic and magnetoelastic behaviour of the magnetostrictive materials. Control of the sign and value of ls by means of alloy composition and by annealing the samples is very important with the view of applications. This paper presents results concerning ls in the as-cast state as well as its dependence on the stress current annealing conditions in low magnetostrictive Co–Fe–Si– B– ŽCr,Ni. amorphous wires. We obtained amorphous wires having low positive or negative saturation magnetostriction by replacement of Co or Fe with small amounts of Cr and
) Corresponding author. Tel.: q40-32-130-680; Fax: q40-32-231-132; E-mail: [email protected]
Ni in nearly zero magnetostrictive Co-rich alloys. The saturation magnetostriction has been determined by means of the small angle magnetisation rotation method ŽSAMR. w3x.
2. Experimental details Amorphous wires with nominal compositions Co 65.25Fe 4.5 Si 12.25 B15 Cr2 Ni 1 and Co 68.15 Fe 2.35 Si 12.5 B15 Cr1 Ni 1 , 125 mm in diameter, were obtained by in-rotating-water spinning method. The small angle magnetisation rotation is determined by applying simultaneously a small amplitude ac magnetic field Ž Hac ., high dc magnetic field Ž Hdc . perpendicular and parallel to the axis of the wire and a tensile stress s . Hdc magnetic field must be high enough to produce the magnetisation saturation of the amorphous wire. The SAMR method is based on detection of the induced voltage V2f Žthe second harmonic of the applied ac magnetic field. in the receiving coil set around the amorphous wire. When a tensile stress s is applied on the wire Žat constant Hac and Hdc magnetic fields., V2f increases or decreases as a consequence of the increment of magnetoelastic anisotropy
0924-4247r99r$ - see front matter q 1999 Elsevier Science S.A. All rights reserved. PII: S 0 9 2 4 - 4 2 4 7 Ž 9 9 . 0 0 0 2 6 - 6
H. Chiriac et al.r Sensors and Actuators 76 (1999) 372–375
373
having a transverse or an axial easy axis, respectively. The change in V2f can be compensated by an adequate modification of Hdc , so that V2f takes the same value as before the stress was applied. The magnetostriction constant is obtained as:
ls s y Ž m 0 Msr3 . Ž D HdcrD s . , for V2 f and Hac s constant
Ž 1.
where m 0 Ms is saturation magnetization. The value of Hdc magnetic field for which SAMR method is suitable should be high enough for V2f Hdc2 to be constant w4x. The transverse magnetic field Hac was obtained by passing through the wire an electric current having 4 kHz frequency and the maximum value less than 50 Arm at the wire surface. The value of ac current was small enough to neglect the increase in temperature of the amorphous wire. The second harmonic V2f was detected using a lock-in amplifier.
3. Results and discussion Fig. 1 illustrates the DTA curves recorded for Co 65.25Fe 4.5 Si 12.25 B 15 Cr2 Ni 1 and Co 68.15 Fe 2.35 Si 12.5 B 15 Cr1 Ni 1 amorphous wires. The DTA measurements were made with a heating rate of 108Crmin. For Co 65.25 Fe 4.5Si 12.25 B15 Cr2 Ni 1 and Co 68.15 Fe 2.35 Si 12.5 B15 Cr1 Ni 1 amorphous wires, the Curie and crystallisation temperatures ŽTC and Tx . are: 513 K, 833 K and 533 K, 823 K, respectively. For Co-rich amorphous wires annealed up to about 20 Armm2 current density, the stabilised average temperature is up to about 450 K.
Fig. 2. The V2f dependence on the applied tensile stress s , with Hdc field as parameter, for amorphous wires tested in the as-cast state: Ža. Co 65.25 Fe 4.5 Si 12.25 B15 Cr2 Ni 1 and Žb. Co 68.15 Fe 2.35 Si 12.5 B 15 Cr1 Ni 1: v 700 Arm; ` 1600 Arm; ' 2400 Arm; ^ 3200 Arm.
Fig. 1. DTA curves for Co 65.25 Fe 4.5 Si 12.25 B15 Cr2 Ni 1 and Co 68.15Fe 2.35 Si 12.5 B15 Cr1 Ni 1 amorphous wires.
In order to establish the measurement conditions for ls determination, we analysed the dependence of the second harmonic V2f on the tensile stress s , Hac and Hdc magnetic fields. Fig. 2Ža. and Žb. shows the dependence of V2f on the applied stress s , with Hdc field as parameter, for Co 65.25Fe 4.5 Si 12.25 B 15 Cr2 Ni 1 and Co 68.15 Fe 2.35 Si 12.5 B 15 Cr1 Ni 1 amorphous wires, tested in the as-cast state. The V2f value decreases when Hdc increases. When s increases, V2f decreases for low positive Co 65.25 Fe 4.5 Si 12.25 B15 Cr2 Ni 1 and increases for low negative Co 68.15 Fe 2.35 Si 12.5 B15 Cr1 Ni 1 amorphous wires. The saturation magnetostriction ls has been evaluated as q0.39 = 10y6 for Co 65.25 Fe 4.5 Si 12.25 B15 Cr2 Ni 1 and y1.15 = 10y6 for Co 68.15 Fe 2.35 Si 12.5 B 15 Cr1 Ni 1 amorphous wires tested in the as-cast state. The measurements were made at 7 kArm of magnetic bias field for which V2f Hdc2 is constant. Having in mind to control the saturation magnetostriction value for these materials, we studied the influence of
374
H. Chiriac et al.r Sensors and Actuators 76 (1999) 372–375
of the structural relaxation is important at low temperature. The maximum value of ls is obtained for annealing temperatures Tann ) Tc, which denotes that these changes are related to the creep-induced magnetic anisotropy that was observed in Co-rich amorphous wires w6x.
4. Conclusions Low positive or negative magnetostrictive amorphous wires were obtained by replacement of Co or Fe with small amounts of Cr and Ni in nearly zero magnetostrictive Co-rich alloys. For Co 65.25 Fe 4.5 Si 12.25 B 15 Cr2 Ni 1 and Co 68.15 Fe 2.35 Si 12.5 B15 Cr1 Ni 1 amorphous wires in the ascast state, the saturation magnetostriction ls has been evaluated as q0.39 = 10y6 and y1.15 = 10y6 , respectively. After stress current treatments at annealing temperatures Tann ) Tc , the saturation magnetostriction ls exhibits the following behaviour: increases about 5 times for Co 65.25 Fe 4.5 Si 12..25 B15 Cr2 Ni 1 amorphous wires; decreases about 2 times for Co 68.15 Fe 2.35 Si 12.5 B15 Cr1 Ni 1 amorphous wires. These materials are very attractive for a wide range of sensing applications especially for those based on the GMI effect and for security system sensors. The tailoring of magnetic and magnetostrictive properties for special applications can be also realised. Fig. 3. The dependence of saturation magnetostriction ls on the current density for 30 min of stress current annealing under 100 MPa, Ža. Co 65.25 Fe 4.5 Si 12.25 B15 Cr2 Ni 1 and Žb. Co 68.15 Fe 2.35 Si 12.5 B 15 Cr1 Ni 1.
stress current annealing on ls . The elevated temperatures were obtained by Joule heating produced by an electric current passing through the amorphous wire. The current density and annealing time were increased up to 40 Armm2 and 35 min, respectively. To evaluate the average temperature inside the samples during the annealing current flowing, the saturation magnetisation was measured as a function of the temperature during conventional furnace treatment and compared to that obtained by Joule heating w5x. Fig. 3Ža. and Žb. shows the changes in saturation magnetostriction for Co 65.25 Fe 4.5 Si 12.25 B 15 Cr 2 Ni 1 and Co 68.15 Fe 2.35 Si 12.5 B15 Cr1 Ni 1 amorphous wires, respectively tested after stress current annealing for 30 min, under 100 MPa tensile stress. For low positive magnetostrictive Co 65.25 Fe 4.5 Si 12.25B 15 Cr2 Ni 1 amorphous wires, ls value remains unchanged up to about 20 Armm2 and then strongly increases. A peak about 5 times higher than in the as-cast state was obtained for about 35 Armm2 . For low negative magnetostrictive Co 68.15 Fe 2.35 Si 12.5 B15 Cr1 Ni 1 amorphous wires, ls decreases about 2 times after stress current annealing. The obtained results can be analysed taking into account the structural relaxation and induced transverse magnetic anisotropy after stress current annealing. The effect
References w1x P.T. Squire, D. Atkinson, S. Atalay, Magnetostrictive and magnetoelastic properties of rapidly quenched wires, IEEE Trans. Magn. 31 Ž1995. 1239–1248. w2x M. Vazquez, A. Hernando, A soft magnetic wire for sensor applications, J. Phys. D: Appl. Phys. 29 Ž1996. 939–949. w3x K. Narita, J. Yamasaki, H. Fukunaga, Measurement of saturation magnetostriction of a thin amorphous ribbon by means of small-angle magnetization rotation, IEEE Trans. Magn. 16 Ž1980. 435–439. w4x A. Mitra, M. Vazquez, Measurement of the saturation magnetostriction constant of amorphous wire, J. Appl. Phys. 67 Ž1990. 4986–4988. w5x M. Knobel, P. Allia P, C. Gomez-Polo, H. Chiriac, M. Vazquez, Joule heating in amorphous metallic wires, J. Phys. D: Appl. Phys. 26 Ž1995. 2398–2403. w6x L. Kraus, M. Vasquez, A. Hernando, Creep-induced magnetic anisotropy in a Co-rich amorphous wire, J. Appl. Phys. 76 Ž1994. 5343– 5348. Horia Chiriac received the BS and PhD degrees in Physics from the ‘Al.I Cuza’ University of Iasi, Romania, in 1962 and 1978, respectively. Currently he is Director of the National Institute of Research and Development for Technical Physics, Iasi and Associate Professor in Physics, ‘Al.I Cuza’ 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 above mentioned materials. Maria Neagu received the BS and PhD degrees in Physics from the ‘Al.I Cuza’ 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 and Development for Technical Physics, Iasi. Her research topics are magnetostrictive materials and sensors based on these materials.
H. Chiriac et al.r Sensors and Actuators 76 (1999) 372–375 Evangelos Hristoforou received the D.Eng. Degree in Electrical Engineering from the Engineering Faculty, University of Patras, Patras, Greece in 1984 and the PhD degree in Electrical Engineering from King’s College London, University of London, UK, in 1991. Currently he is Head of the Metrology Laboratory, Faculty of Engineering Applications, Technological and Educational Institution of Chalkis, Euboea, Greece. His research topics are sensors and actuators based on magnetic materials.
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