Materials Science and Engineering A 375–377 (2004) 1137–1139 Magnetostrictive properties of Fe 40 Ni 38 Mo 4 B 18 alloy Roman Szewczyk a,∗ , Adam Bie ´ nkowski b,1 , Aleksandra Kolano-Burian c a Industrial Research Institute for Automation and Measurements, Al. Jerozolimskie 202, 02-486 Warsaw, Poland b Institute of Metrology and Measuring Systems, Warsaw University of Technology, sw. A. Boboli 8, 02-525 Warsaw, Poland c Institute of Non-ferrous Metals, Sowi´ nskiego 5, 44-100 Gliwice, Poland Abstract Magnetostrictive properties as initial curve and major and minor magnetostriction hysteresis butterﬂy loops of Fe 40 Ni 38 Mo 4 B 18 as-quenched amorphous alloy as a function of quasi-static magnetic ﬁeld were investigated. The strip amorphous sample and semiconductor strain gauges were used. The measurements were performed in solenoid and Helmholtz coils, which enables sample to be magnetised in two perpendicular directions. Minor magnetostriction loops after each returning to zero of the magnetic ﬁeld and polarised magnetostriction loops with the alternating magnetic ﬁeld are shown. © 2003 Elsevier B.V. All rights reserved. Keywords: Magnetostriction; Amorphous alloys 1. Introduction Magnetostrictive properties of amorphous alloys are im- portant from both physical and practical point of view. From physical point of view, the results of the investigation of the magnetostrictive properties can be helpful in analyzing some fundamental questions concerning magnetic phenomena in amorphous alloys [1]. Moreover, magnetostrictive effect can be utilized in construction of different sensors and actuators [2], especially for micro-scale applications. For this reason, magnetostrictive properties of amorphous alloys have been extensively studied for over 30 years [3]. This paper presents results of magnetostrictive properties of the Fe 40 Ni 38 Mo 4 B 18 amorphous alloy in as quenched state. This alloy composition is very popular in sensor ap- plications. In spite of this fact, complete information about its magnetostrictive properties, especially minor hysteresis loops, seems to be still not presented. 2. Method of investigation Among the direct methods of measurements of the mag- netostriction, the strain gauges are commonly used [4]. ∗ Corresponding author. Tel.: +48-22-8740280; fax: +48-22-8740209. E-mail addresses: szewczyk@mchtr.pw.edu.pl (R. Szewczyk), bi- enko@mchtr.pw.edu.pl (A. Bie´ nkowski). 1 Tel.: +48-22-6608551; fax: +48-22-8490395. Moreover, this method creates the possibility of measuring the magnetostriction under mechanical stresses. Because the values of λ s of the investigated amorphous alloys are small, it was necessary to use very sensitive strain gauges. Kovo AP 120-3-12 semiconductor gauges proved to be sufﬁcient for this purpose. The gauges have a 120 gauge factor and a resistance about 120 . In the case of mea- surement of the magnetostriction of amorphous alloys, greater measuring accuracy is required from semiconductor gauges. For this reason, a correction factor of non-linearity of semiconductor strain gauge should be calculated [5]. The semiconductor strain gauges were conjucted with AC Wheastone bridge. The investigation of magnetostrictive properties of the Fe 40 Ni 38 Mo 4 B 18 as quenched amorphous alloy strips was carried out at room temperature. The strip was 100 mm long, 8 mm wide and 25 m thick. The measuring installation used for applying the magne- tizing ﬁeld is presented in Fig. 1. The magnetizing ﬁeld in direction of the strip was created by solenoid. For applying the magnetizing ﬁeld perpendicularly to the strip direction, the Helmholtz coils were used. The magnetizing coils were excited by NF-4025 Electronic Instruments power ampliﬁer. Ampliﬁer was driven by digitally controlled function gener- ator RMD-2a, constructed especially for magnetic measure- ments. In case of strain gauges used for measurement of magne- tostriction of amorphous alloy strips, loading of the magnetic material by strain gauge cannot be neglected [4]. For this reason, value of displacement ε measured by strain gauge 0921-5093/$ – see front matter © 2003 Elsevier B.V. All rights reserved. doi:10.1016/j.msea.2003.10.197