ARTICLE IN PRESS Journal of Magnetism and Magnetic Materials 304 (2006) e868–e870 www.elsevier.com/locate/jmmm Soft magnetic behaviour in amorphous and nanocrystalline Fe73.5ÀxMnxSi13.5B9Nb3Cu1 (x ¼ 1, 3, 5) alloys N.D Thoa, N Chaua, S.C Yub,Ã, H.B Leec, L.A Tuanc, N.Q Hoaa a Center for Materials Science and Faculty of Physics, Hanoi University of Science, 334 NguyenTrai, Hanoi, Vietnam b Department of Physics, Chungbuk National University, Cheongju 361-763, Republic of Korea c Departement of Physics, Kongju NationalUniversity, Kongju 314-701, Republic of Korea Available online 27 March 2006 Abstract Amorphous ribbons Fe73.5ÀxMnxSi13.5Nb3Cu1 (x ¼ 1, 3, 5) were prepared by rapid quenching on a single rotated copper wheel The X-ray patterns show that the as-cast samples are amorphous The measurements of thermomagnetic curves indicated that the Curie temperature of the amorphous phase of the samples decreased with increasing Mn content The optimal heat treatment was performed at Ta ¼ 535 1C for h and showed that the ultrasoft magnetic properties of nanocomposite materials were obtained The frequency dependence of magnetoimpedance was measured in the frequency range of 1–10 MHz and at a fixed current of 10 mA The correlation between the MI effect and the soft magnetic properties is discussed r 2006 Elsevier B.V All rights reserved PACS: 75.50 Tt Keywords: Nanocrystalline; Amorphous; Magnetoimpedance; Permeability Soft magnetic properties of Fe-rich nanocrystalline alloy Fe73.5Si13.5B9Nb3Cu1, namely, FINEMETs materials [1] have been extensively studied during the last decade [2] The increased interest in the study of the alloys arises from a wide applications found in saturable reactor, generators, transformer and magnetic sensors [3] The influence of partial substitution of Fe with various alloying elements (Co [4], Cr [5]) in Fe73.5Si13.5B9Nb3Cu1 alloy has been widely investigated They found that the partial substitution of Fe by Cr could improve the mechanical or electrical properties without deteriorating magnetic properties while substitution for Fe by Co leads to the increase of magnetic moment and Curie point of the precipitated crystalline phase Recently, it was reported that the partial substitution of Fe by Mn in Fe-based amorphous alloys can also improve the coupling between grains and AC permeability, but leads to reduction of the exchange coupling between the crystalline and residual amorphous phase [6] ÃCorresponding author Tel.: +82 43 2612269; fax: +82 43 2756415 E-mail address: scyu@chungbuk.ac.kr (S.C Yu) 0304-8853/$ - see front matter r 2006 Elsevier B.V All rights reserved doi:10.1016/j.jmmm.2006.03.020 The aim of the present work is to investigate the influence of partial substitution of Fe by Mn on the magnetic properties of the Fe73.5ÀxMnxSi13.5B9Nb3Cu1 (x ¼ 1, 3, 5) alloys The correlation between the MI effect and soft magnetic properties of these ribbons is also discussed Amorphous Fe73.5ÀxMnxSi13.5B9Nb3Cu1 (x ¼ 1, 3, 5) alloys were prepared by melt–spinning technique The ribbon is mm wide and about 20 mm thick The structure of the as-cast and annealed samples was examined by a Bruker 5005 X-ray diffractometer The crystallization phases were examined by differential scanning calorimetry (DSC) using SDT 2960 TA Instrument The magnetic properties of the ribbon were measured in a DMS 880 VSM and a Walker Permagraph AMH 20 For the MI measurement the external field applied by a solenoid can be swept through the entire cycle equally divided by 800 intervals from 300 to 300 Oe The frequency of the MI measurement ranged from to 10 MHz, and the AC current was fixed at 10 mA for all measurements Firstly, we examined the structure of the as-quenched samples by using OLE_LINK1XRDOLE_LINK1y ¼ 451 indicating the amorphous nature of the as-cast samples ARTICLE IN PRESS N.D Tho et al / Journal of Magnetism and Magnetic Materials 304 (2006) e868–e870 564°C 676°C 673°C Heat Flow (a.u.) 563°C 671°C 562°C x=5 x=3 x=1 150 300 450 600 Temperature (°C) 750 900 Fig DSC patterns of as-cast Fe73.5ÀxMnxSi13.5B9Nb3Cu1 (x ¼ 1, 3, 5) ribbons 120 Fe72.5Mn1Si13.5Nb3B9Cu1 H = 20 Oe 90 M (emu/g) We carried out DSC measurements in order to characterize the crystallization process and found out the proper annealing temperature for the as-quenched amorphous ribbon Fig shows the DSC curves of the as-quenched amorphous ribbon with a heating rate of 20 1C/min and from room temperature to 800 1C As observed in Fig 1, the crystallization process of the investigated alloys take place in two main steps The first one corresponds to the nanocrystallization of the a-Fe(Si) soft magnetic phase, while the second is related to the appearance of boride-type phases (Fe3B or Fe2B) and recrystallization phenomena [6] The crystallization temperature of the a-Fe(Si) phase (Tp1) in all samples studied is higher than that of the original FINEMETs alloy It shows that the addition of Mn clearly exerts a stabilizing effect on the amorphous alloys against nanocrystallization As observed also in Fig 1, the Tp1 increases almost linearly with Mn content in the range of the composition studied This implies that the existence of Mn to certain extent weakens the diffusion process to form the crystalline phase We used the Kissinger method [7] to quantify the crystallization kinetics of a continuous heating and found out the crystallization activation energy values of a-Fe(Si) phase in the present alloys The values of activation energy were found to decrease from 3.1 eV (x ¼ 1) to 2.8 eV (x ¼ 3) and to 2.6 eV (x ¼ 5) (not shown here) for the a-Fe(Si) phase In order to study the crystallization kinetics, we measured thermomagnetic curves of the amorphous samples Fig shows the magnetization versus temperature for the sample with x ¼ From the thermomagnetic curves, it can be seen that the Curie temperature of amorphous phase of the samples decreases with increasing e869 60 (2) (1) 30 (a) 0 150 300 450 T (°C) 600 750 Fig Thermomagnetic curves of ribbon with x ¼ (1: heating cycle, 2: cooling cycle) of Mn content, namely TC ¼ 342 1C (x ¼ 1), TC ¼ 310 1C (x ¼ 3) and TC ¼ 281 1C (x ¼ 5) It means that the Curie temperature of the amorphous phase in the samples studied is reduced because Mn interacts antiferromagnetically with Fe as reported in Ref [8] The influence of partial substitution of Fe by Mn and heat treatments on the magnetic properties was also studied by measurements of magnetic hysteresis loops and magnetization curves It was found that the presence of Mn has a noticeable effect on the shape of the magnetic hysteresis loops, causing a decrease in coercivity and maximum magnetization in the as-quenched amorphous samples and annealed samples The magnetization curves were measured for both as-cast as well as annealed samples (not shown here) The results indicated that saturation magnetization also decreases with increasing Mn content The magnetoimpedance ratio (MIR), can be defined as DZ/Z (%) ¼ Z(H)/Z(Hmax)À1, where Hmax is external magnetic field sufficient to saturate the impedance and equals to 300 Oe in the present study The giant magnetoimpedance effect can be observed only in ultrasoft magnetic materials with nearly zero magnetostriction constant, nearly zero coercivity, and high circumferential permeability The nearly zero MIR value in as-quenched samples is evident that the samples are not ultrasoft However, the maximum MIR value increases drastically in the samples annealed at 535 1C It is indicated that the samples are softened by nanocrystallization, an example shown in Fig with x ¼ The results obtained show that the values of MIR increase with increasing Mn content The permeability ratio (PR), is also plotted in Fig as a function of the external field One notes that the changes of the magnetoimpedance are much related to the changes of ARTICLE IN PRESS N.D Tho et al / Journal of Magnetism and Magnetic Materials 304 (2006) e868–e870 e870 40 50 Ta = 535°C in 1h Fe72.5Mn1Si13.5B9Nb3Cu1 10 mA 20 mA 30 mA 40 35 2M Hz 3M Hz 30 f=1MHz x=1 4M Hz 5M Hz 25 30 ∆µ/µ (%) ∆Z/Z (%) 1M Hz Ta = 535°C in 1h 20 i = 10 mA 20 15 10 10 -300 -200 -100 H (Oe) 100 200 300 Fig MIR measured at MHz of the sample with x ¼ as a function of the external dc field at various ac drive fields -300 -200 -100 H (Oe) 100 200 300 Fig The PR vs the external field H for sample with x ¼ 1, annealed at 535 1C for h longitudinal permeability in the presence of an external field The sharpness of PR curves after annealing implies the decrease of the local anisotropy distribution by nanocrystallization This behaviour is helpful to examine the soft magnetic properties of the present alloys References Research at Chungbuk National University was supported by Korea Research Fundamental Grant no KRF2003-05-C00018 Research at Center for Materials Science was supported by Vietnam National Fundamental Research Program Grant no.421004 [5] [1] [2] [3] [4] [6] [7] [8] Y Yoshizawa, S Oguma, K Yamauchi, J Appl Phys 64 (1998) 6044 G Herzer, Master Sci Eng A 133 (1999) D.C Jiles, Acta Master 51 (2003) 5907 N Chau, N.X Chien, N.Q Hoa, P.Q Niem, N.H Luong, N.D Tho, V.V Hiep, J Magn Magn Mater 282 (2004) 174 A Pardo, E Otero, M.C Merino, M.D Lopez, M Vazquez Crros Sci 43 (2001) 689 C Gomez-Polo, J.I Perez-Landazabal, V Recarte, P.M Zelis, Y.F Li, M Vazquez, J Magn Magn Mater 290–291 (2005) 1517 L.V Meisel, P.J Cote, Acta metal 31 (1983) 1053 K Ashok, I Sinha, Appl Phys 42 (1971) 338  ... annealed at 535 1C It is indicated that the samples are softened by nanocrystallization, an example shown in Fig with x ¼ The results obtained show that the values of MIR increase with increasing... crystalline phase We used the Kissinger method [7] to quantify the crystallization kinetics of a continuous heating and found out the crystallization activation energy values of a-Fe(Si) phase in. .. (Tp1) in all samples studied is higher than that of the original FINEMETs alloy It shows that the addition of Mn clearly exerts a stabilizing effect on the amorphous alloys against nanocrystallization