Structural, magnetic and electrical investigations of Fe_1─XMn_X (0 ≤ x ≤ 0.39) alloy nanowires via electrodeposition in AAO templates

Highlights

• The FeMn (Fe_1─XMn_X (0 ≤ x ≤ 0.39)) alloy nanowires are synthesized by AC electrodeposition method.

• The physical properties of FeMn alloy nanowires are tuned by changing the concentration of Mn.

• The SEM images confirmed that the average diameter of nanowires are 50 nm.

• The grain size was increased from 38 to 53 nm as Mn contents increased in the NWs.

• The coercivity ($H_c$) and saturation magnetization ($M_s$) were decreased with increase in concentration of Mn.

Abstract

The Fe_1─XMn_X (0 ≤ x ≤ 0.39) nanowire (NW) arrays were synthesized through anodic aluminum oxide (AAO) template-based electrodeposition method. The elemental composition of the NWs was varied by changing the Mn-ions concentration in the electrochemical bath during electrodeposition. Energy Dispersive X-rays Spectroscopy (EDX) spectrums confirmed the Mn contents, that was increased in the NWs from 0 to 39 with respect to increase in Mn-ion concentration in the electrolyte. The X-ray diffraction (XRD) patterns exhibited the NWs were crystallized into the body-centered cubic (bcc) structure. Furthermore, the lattice parameter of NWs decreased as Mn content increased in the NWs whereas the increasing trend in grain size was observed. The magnetic properties of NWs were determined by recording MH-loops at room temperature with applied magnetic field in parallel ($\parallel$) and perpendicular ($\perp$) direction to the long-axis of NWs. The MH-loops revealed the existence of strong magnetic anisotropy and anisotropy field ($H_k$) that was determined by the Anisotropy Field Distribution (AFD) method. A decreasing trend in the coercivity ($H_c$), saturation magnetization ($M_s$) and anisotropy field ($H_k$) was observed as a function of Mn contents in FeMn NWs. The ZFC-FC curves were also recorded with 1kOe applied magnetic field, which demonstrated the ferromagnetic behavior and exhibited the blocking temperature was increased (Fe NWs ~ 300 K, Fe_0.82Mn_0.18 NWs ~ 330 K, and Fe_0.61Mn_0.39 NWs > 350 K) with the increase of Mn content. Moreover, the conductivity and mobility of the NWs were also decreased that were analyzed through four-probe Hall techniques.

Introduction

From the past few decades, many researchers have focused their research interest on one-dimensional (1D) nanostructures such as NWs, because the properties of these nanostructures can be easily tuned by varying the chemical composition, length and diameter [[1], [2], [3]]. The NWs exhibit a significantly different domain walls dynamics in contrast to domain walls in thin films and also possess a controllable domain wall spin structure with their diameter [4]. In addition, the 1D nanostructure can be easily synthesized with control geometry by a well-known AAO template-based electrodeposition method as compared to other nanostructures [2].

Recently, the shape memory alloys got weightage, concerning its application. C. M. Wayman discovered the shape memory effect in Fe-based alloy [5]. The shape memory and superelasticity are affected through Fe-based nanostructures such as FeMnSi and FeMn alloys that produced numerous interest due to their implementation in sensors, magnetic random access memory (MRAM) and other several potential applications [6,7]. Particularly, to enhance the efficiency of Spintronics devices such as race-track memories by using NWs synthesized through electrodeposition is one of the most active current research field [4,8]. In future, the Spintronics devices that require spin-valves to inject the spin-polarized current, need to fix one of the ferromagnetic material to anti-ferromagnetic which form their specific structure [9]. The iron-based ferromagnetic material, couple with non-ferromagnetic like manganese at the nanoscale, shows magnetically soft composite due to interfacial exchange coupling [10,11].

The existence of the biological alloys, such as Fe-based (FeMn) biodegradable alloy, seems to be more suitable than nickel-based; the anterior being necessary for humanoid [12] and the nickel classified as a carcinogenic and a toxic [13]. Manganese is not a toxic in the cardiovascular system at a higher ratio [14]. The Mn contents in such controllable degradation that could be acknowledged to be less than their toxic level in blood [15].The ferromagnetic Fe NWs give rise to a new technology by making alloy with non-ferromagnetic material; Mn to form FeMn that were deposited through electrodeposition in AAO templates. The aligned and uniform NWs in AAO templates have been used in many technological applications, such as the growth of vertical devices used for storage with high aspect ratio. Here, limited research has been done on FeMn alloys, because of difficulty to deposit Mn with Fe electrochemically [16,17]. Hence, in present research, first we synthesized FeMn alloy NWs in AAO templates through electrodeposition and then analyzed its structural, magnetic and electrical properties in detail that will enhance the properties of spintronics devices in the future prospectus.