Structure and magnetic properties of Fe1−xCox nanowires in self-assembled arrays

Abstract

a b s t r a c tFe 1−x Co x nanowires in self-assembled arrays with varying compositions were produced by the templateassisted pulsed electrochemical deposition method. The structural and magnetic properties of the arrays were investigated using several experimental techniques. TEM analyses indicated that the nanowires were regular, uniform, 8 m in length and 50 nm in diameter. The results of X-ray diffraction indicated that the body-centered-cubic (bcc) (␣), face-centered-cubic (fcc) (␥), and hexagonal-close-packed (hcp) () Fe-Co phases appeared in different compositions. Magnetic measurements showed that the coercivity and squareness of the hysteresis loops of the Fe 1−x Co x changed with their compositions, which may be attributable to shape anisotropy. The room temperature 57 Fe Mössbauer spectra of the arrays of the Fe 1−x Co x nanowires revealed strong shape anisotropy.

Controlled Electrodeposition and Magnetic Properties of Co35Fe65Nanowires with High Saturation Magnetization

“…Unfortunately, some complexing organic non-saccharin additives in electrodeposition of TM alloys, caused more than 40% decrease of B s -value due to the incorporation of oxygen compounds into the deposit. [34][35][36][37] Use of ascorbic acid (AA) as a reducing agent for Fe +3 ions in the preparation of CoFe nanowires, [15][16][17][18][19][20][21][22][23][24][25][26] is efficient for deaerated plating solution in the short term. However, over longer times accumulated dehydroascorbic acid (DHAA), formed in the redox reaction, is subjected to hydrolysis giving rise to several possible bidentate nucleophiles.…”

“…If SR∼1.0, it means that there is no anomalous codeposition, which is consistent with previous results. 18 The typical SR values obtained at the controlled potential of E = −1.1 V/SCE are increased gradually with increasing of Fe +2 /Co +2 ions ratio in solution from SR = 1.04 (for ions ratio of 0.14) to SR = 1.58 (for ions ratio of 2.0). These results were used in subsequent pulsed potential deposition of nanowires under quiescent conditions obtained from solution with ions ratio, Fe +2 /Co +2 = 2.0, by varying the potential during time-on and keeping the reverse potential constant during time-off at E = −0.7 V/SCE.…”

“…[28][29][30][31] In industrial electrodeposition of 2.4 T CoFe films the problem of accumulation of Fe +3 ions in solution is solved by continues chemical reduction of Fe +3 to Fe +2 ions. In laboratory preparation of CoFe nanowire arrays ascorbic acid can be used as a reducing agent for Fe +3 ions, [15][16][17][18][19][20][21][22][23][24][25][26][27] and this will be discussed later in the text. The second major challenge in the electrodeposition of CoFe alloys is that they experience a phenomena known as an anomalous codeposition, which is characterized by the anomaly that the less noble metal, i.e.…”

“…14 In the last decade, methods of electrodeposition, as well as the structural and magnetic properties of CoFe nanowire arrays have been extensively investigatied, [15][16][17][18][19][20][21][22][23][24][25][26][27] since CoFe materials have high * Electrochemical Society Member. z E-mail: tabakovicibro@gmail.com saturation magnetization, low coercivity and high magnetic shape anisotropy.…”

“…13 Therefore, controlled deposition to obtain magnetic nanostructures with a high saturation magnetization could be promising for new T2 MRI contrast agents. 14 In the last decade, methods of electrodeposition, as well as the structural and magnetic properties of CoFe nanowire arrays have been extensively investigatied, [15][16][17][18][19][20][21][22][23][24][25][26][27] since CoFe materials have high saturation magnetization, low coercivity and high magnetic shape anisotropy. In order to produce pure CoFe alloy with targeted composition and very high saturation magnetization (B s ≥ 2.4 T), one has to overcome two major challenges.…”