Influence of Co Addition on Magnetic Properties and Glass Formation of Fe-based Amorphous Alloys
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1048-Z08-08
Influence of Co Addition on Magnetic Properties and Glass Formation of Fe-based Amorphous Alloys Rafael Piccin1, Paola Tiberto2, Nicoleta Lupu3, Horia Chiriac3, and Marcello Baricco1 1 Dipartimento di Chimica IFM and NIS, Università di Torino, Via P.Giuria, 9, Torino, 10125, Italy 2 Istituto Nazionale di Ricerca Metrologica INRIM, Strada delle Cacce 91, Torino, 10135, Italy 3 National Institute of Research and Development for Technical Physics, 47 Mangeron Blvd., Iasi, 700050, Romania ABSTRACT In the present work, the influence of Co addition on the glass forming ability (GFA) and magnetic properties of the ((Fe1-xCox)75B20Si5)93Nb4Y3 (x = 0, 0.2, 0.4, 0.5, 0.6, 0.8, 1) alloy is evaluated. Ribbons and 1 mm diameter ingots were prepared by melt-spinning technique and Cumold injection casting technique, respectively. The presence of the amorphous phase was confirmed through X-ray diffraction and high temperature differential scanning calorimetry (HTDSC). Rapid solidification leads to fully amorphous ribbons for all compositions. Conversely, ingots with Co content with x > 0.5 present boride crystalline phases. Magnetization measurements were performed by means of vibration sample magnetometer in a temperature range from room temperature to 850 °C in order to determine the Curie temperature (TC) of the amorphous phase and to follow the formation of magnetic phases at high temperatures. In addition, hysteresis loops measurements were carried out to study the magnetic response of the samples. Co substitution until x = 0.5 is seen to simultaneously induce in the as-cast ingots a decrease of coercive field from 52 to around 10 A/m and an increase of the Curie temperature of the amorphous phase from 480 to 700 K. A maximum saturation magnetization value of 123 emu/g was observed in the sample having x = 0.2. The role of Co substitution on glass formation is discussed on the basis of crystallization and melting behaviors, analyzed by HT-DSC. Magnetic properties are correlated with the presence of crystalline phases and their microstructures. INTRODUCTION Ferromagnetic amorphous alloys based on transition metal and metalloid elements have been extensively studied in recent years due to their outstanding magnetic properties [1]. Such properties resulted to provide relevant contribution to technological progress, such as in power devices, information handling technology and magnetic sensors. However, the glass forming ability (GFA) of transition metals based alloys is quite limited when compared to Zr, Pd, and Mg-based alloys [2], stating a critical thickness of ~ 100 µm for Fe-based ribbons that can limit their field of applications. To improve the GFA of such systems, in order to obtain a bulk metallic glass (BMG), a common approach is the minor alloying addition technique [3]. Nb and Y have shown to be good candidates as alloying elements for Fe-based alloys while B and Si atoms are used to optimize both the GFA and soft magnetic properties [4]. Furthermore, Co additions can improve the soft magnetic properties
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