Aqueous electrodeposition of iron group-vanadium binary alloys

Article abstract of DOI:10.1016/j.electacta.2005.01.047

Electrodeposition of binary iron group (IG)-vanadium (V) alloys from aqueous citrate solutions was investigated. Addition of NH₃(aq.) and increasing solution pH resulted in increased deposit V content, but non-metallic deposits were obtained at solution pH > 7. Increasing current density resulted in an almost linear decrease in V content and a sharp increase in hydrogen evolution (decreased current efficiency). In general, the amount of V deposited with the IG metal increased as follows: Ni < Fe ≤ Co. XRD spectra indicated that preferred orientations from 25 °C solutions were not displaced by elevated temperature deposits. Changes in orientation may contribute to the deposit magnetic properties; e.g., Co-V deposits with (1 0 0) planes exhibit harder magnetization than deposits with (0 0 2) planes.

Full text of DOI:10.1016/j.electacta.2005.01.047

Electrochimica Acta 50 (2005) 4335–4343
Aqueous electrodeposition of iron group–vanadium binary alloys
B.Y. Yoo, M. Schwartz, K. Nobe∗,1
Department of Chemical Engineering, University of California, Los Angeles, CA 90095-1592, USA
Received 12 July 2004; received in revised form 10 January 2005; accepted 30 January 2005
Available online 7 April 2005
Abstract
Electrodeposition of binary iron group (IG)–vanadium (V) alloys from aqueous citrate solutions was investigated. Addition of NH3(aq.)
and increasing solution pH resulted in increased deposit V content, but non-metallic deposits were obtained at solution pH > 7. Increasing
current density resulted in an almost linear decrease in V content and a sharp increase in hydrogen evolution (decreased current efficiency). In
general, the amount of V deposited with the IG metal increased as follows: Ni < Fe ꢀ Co. XRD spectra indicated that preferred orientations
from 25 ◦C solutions were not displaced by elevated temperature deposits. Changes in orientation may contribute to the deposit magnetic
properties; e.g., Co–V deposits with (1 0 0) planes exhibit harder magnetization than deposits with (0 0 2) planes.
© 2005 Elsevier Ltd. All rights reserved.
Keywords: Iron-group; Vanadium; Magnetic alloys
1. Introduction
trodeposition rate co-deposits at a much slower rate than the
other metal. Since Brenner, there has been extensive work on
anomalous co-deposition because it is crucial to take this phe-
nomenon into account in Permalloy’s manufacturing process
[6]. For example, Talbot and co-workers have investigated
co-deposition of the iron group binary alloys [7–9]. Dahms
and Croll [10] had earlier proposed an explanation for anoma-
lous co-deposition of Ni–Fe alloys in which adsorbed ferrous
hydroxide species retard the deposition of Ni. Hessemi and
Tobias [11] pointed out the importance of IG hydroxide ions
in anomalous co-deposition. Additional models involving IG
hydroxide ions have also been proposed by Talbot and co-
workers [12,13] and Matlosz [14]. In addition to the current
interest in iron group alloys for their magnetic properties,
Invar (64Fe36Ni) and Super Invar (64Fe31Ni5Co) are im-
portant for their low coefficient of thermal expansion [15,16].
There has been considerable effort directed to develop
alloys with soft magnetic properties superior to Permalloy
due to rapid advances in areal densities of computer hard
disks. Liao [17,18] has reported that 90Co10Fe electrode-
posits had twice the magnetic saturation of Permalloy,
low coercivity and high magnetic permeability. However,
Co–Fe alloys have low corrosion resistance and electrical
resistivity; deposits are too brittle for fabrication of suitable
Iron group alloys have generated considerable interest for
a number of years due to their magnetic properties. Brenner
[1] in his seminal treatise on the electrodeposition of alloys
reviewed the literature of the iron group alloys up to the
early 1960s. Srimathi et al. [2] provided a comprehensive
review of magnetic iron group alloy electrodeposits up to
1980. Since that time there have been numerous papers on
the electrodeposition of iron group alloys because of their
importance in the microelectronics industry, particularly in
computer technology. Special emphasis had been directed to
Permalloy (80Ni20Fe) because of its attractive soft magnetic
properties for computer memory applications [3–5].
One unusual phenomenon encountered in the electrode-
position of Permalloy and other iron group alloys is the
so-called anomalous co-deposition. Brenner discusses this
phenomenon in which the less noble metal co-deposits at
a faster rate than the more noble metal [1]. A more general
representation is that the metal with the faster individual elec-
∗
Corresponding author. Tel.: +1 310 8252447; fax: +1 310 8253458.
E-mail address: nobe@seas.ucla.edu (K. Nobe).
ISE member.
1
0013-4686/$ – see front matter © 2005 Elsevier Ltd. All rights reserved.
doi:10.1016/j.electacta.2005.01.047

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B.Y. Yoo et al. / Electrochimica Acta 50 (2005) 4335–4343
Table 1
geometrical forms. There has been much work directed to
overcome shortcomings of the soft magnetic properties of
90Co10Fe by introducing a third element, such as B, Cu and
V [19–21]. Vanadium, like W, Mo and the rare earth metals,
has not been electrodeposited from aqueous media. How-
ever, several workers have successfully alloyed iron group
metals with W and Mo by electrodeposition from aqueous
baths (see refs in [21c]). Bulk Permendur (50Fe50Co),
2V-Permendur (49Fe49Co2V) and Supermendur (purified
49Fe49Co2V) have excellent soft magnetic properties but
have not had extensive commercial applications due to
expensive processing costs. Because of the current interest
in magnetic thin films for microelectromechanical systems
(MEMS) and nanoelectromechanical systems (NEMS) ap-
plications, renewed electrodeposition activity in this group
of soft magnetic ternary alloys, which are characterized by
high magnetic saturation, permeability, Curie temperatures
and low coercivity, seems justified. Electrodeposition has
advantages over other deposition technologies; these include
cost effectiveness, ease of fabrication and control.
In their review of the magnetic properties of Fe–Co
alloys, Chin and Wernick [22] indicated that adding Co to
Fe increases Bs and reported that a Bs of 2.45 T had been ob-
tained for 65Fe35Co; this is the highest magnetic saturation
(Bs) that had been reported, thus far, in the literature. This
Bs value has also been given for Permendur (50Fe50Co)
in Chen’s table 6.6 [23]. In addition to the reviews listed
in [21c] (e.g. Refs. [13–17]), other literature reviews of
work on vanadium alloys include Refs. [24,25]. Magnetic
properties for Permendur, 2V-Permendur and Supermendur
reported in the references cited are summarized below:
Bath Composition for Electrodeposition of Co–V, Fe–V and Ni–V
Reagent
Co–V bath
(M)
Fe–V bath
(M)
Ni–V bath
(M)
Cobalt chloride
Ferrous chloride
Nickel chloride
Vanadyl sulfate
Ammonium chloride
Ammonium citrate
0.3
0
0
0.17
1.1
0.34
0
0.15
0
0.32
1.1
0.34
0
0
0.3
0.17
1.1
0.34
lected because of its higher solubility in water and lower ox-
idation state compared to other soluble vanadium salts, such
as ammonium vanadate. Cobaltous, ferrous and nickelous
chlorides were chosen as the iron group metal salts with the
bath pH varied from 5.5 to 7.0. To prepare stable baths, the
mixing sequence of the chemicals is very important to avoid
formation of precipitates.
The mixing sequence is as follows: Initially, cobalt, iron or
nickel salt was dissolved in deionized water and mixed with
ammonium chloride and the complexer, ammonium citrate.
Then, the solution pH was increased up to ∼8 by the addition
of NH3(aq.) (74 mL/L from a 14.8N stock solution). With
the addition of the vanadium salt, solution pH decreased to
around 6.5. Final pH was adjusted by addition of either HCl
or KOH (solution volume was 100 mL).
The films were electrodeposited by varying current den-
sity from 1 to 50 mA/cm2. Direct current was supplied by a
PAR potentiostat (model 273). Brass panels (6 cm2) served
as cathodes; anodes were sheets of the appropriate iron group
metals. Electrodeposition was carried out at room tempera-
ture, unless otherwise noted, and the solution was not agitated
during electrodeposition.
The brass panels were first cleaned with ALCONOX, fol-
lowed by dipping in a 5 vol.% HCl solution to remove or-
ganic impurities and the incipient surface oxide film. After
cleaning the surface, the brass substrate was dried, weighed
(before and after plating for CE calculations), then activated
by immersion in 20 vol.% HCl for 1 min.
Permendur
7
2 V-Permendur
25
Supermendur
25
Elect. resistivity
(␮ꢀ cm)
Magnetic
saturation, Bs
(T)
2.45
2.40
2.40
Remanence, Br
(T)
1.40
1.50
2.22
Maximum
permeability,
µm
5000
4000–8000
92500
After inspection with an optical microscope (600×), the
deposits were dissolved in nitric acid. The composition of
the electrodeposits was determined by atomic adsorption
spectrophotometry (AA) (Perkin-Elmer, model 280) and en-
ergy dispersive spectroscopy (EDS). Microstructure was ana-
lyzed with X-ray diffraction (XRD) and surface morphology
with scanning electron microscopy (SEM). Magnetic proper-
ties were measured using a vibrating sample magnetometer
(VSM, ADE Tech, Model 1660).
Coercivity, Hc,
(Oe)
2
5
0.2
The present paper focuses on the electrodeposition of
IG–V binary alloys; a subsequent paper will provide experi-
mental results of the investigation on the electrodepositon of
ternary Co–Fe–V alloys.
2. Experimental
3. Results and discussion
Co–V, Fe–V and Ni–V alloys were electrodeposited from
citrate baths, compositions of which are given in Table 1,
unless noted otherwise. Ammonium chloride was added as
a conducting salt, and also to increase the concentration of
NH4+ ions in the solution. Vanadyl sulfate (VOSO4) was se-
3.1. Co–V electrodeposits
Fig. 1 shows EDS spectra of Co–V deposits obtained from
solution compositions (Table 1) and deposition conditions

B.Y. Yoo et al. / Electrochimica Acta 50 (2005) 4335–4343
4337
Fig. 2. Effect of pH on the composition and current efficiency of Co–V
electrodeposits; CD: 3 mA/cm2.
Increasing the solution pH from 5.0 to 6.0 (Fig. 2) re-
sulted in a linear increase in deposit V content from 2.3 to
8.6 wt.%; increasing solution pH to 6.5 further increased V
content slightly (9.2 wt.%). The CE increased from 57 to
72%. With solution pH > 6.5, dull, dark deposits were ob-
tained, indicating the presence of oxides and/or hydroxides.
Subsequent deposits were made from solutions maintained
at pH 6.0. In previous studies [21c], no V was detected in Co
deposits from slightly differing solution composition at pH
5.5 and only ∼1 wt.% V in deposits from pH 7.0 solutions.
This difference with present results may be attributed to the
inhibiting presence of borate and the uncontrolled additions
of NH3(aq.) to maintain pH. Further, solution preparation
(sequence of mixing) differed from the present procedure.
Fig. 3 shows the influence of applied current densities
(CD) on the deposit Co and V contents. Between 1 and
10 mA cm−2 there is a sharp increase in deposit Co content
with a corresponding decrease in deposit V content. These
‘trends’arereducedwithCDs > 10 mA cm−2;at50 mA cm−2
the deposit composition is 98.8 wt.% Co and 1.2 wt.% V as
Fig. 1. EDS analysis of Co–V alloys electrodeposited with solution pH ad-
justed by KOH (a) or NH3 (b); pH 6.0, CD: 5 mA/cm2.
with and without addition of NH3 (aq.). Solutions contain-
ing NH3 (Fig. 1b) resulted in deposit V content ∼4.3 wt.%,
whereas those devoid of NH3 (Fig. 1a) resulted in deposits
with very low V content (0.5 wt.%). The presence of NH3
(aq.) appears to function concomitantly with citrate as com-
plexing agent. There seems to be an optimum NH3 concen-
tration, above which the deposit V content is increased but
results in non-metallic deposits.
Doubling the vanadyl sulfate (VOSO4) concentration
from 0.1 to 0.2 M (Co = 0.3 M) resulted in a slight increase in
deposit V content (Table 2). The cathode current efficiency
(CE) reached a maximum (71%) at 0.17 M VOSO4 concen-
tration. In subsequent studies, the VOSO4 and CoCl2 con-
centrations were maintained at 0.17 and 0.3 M, respectively.
Table 2
Effect of VO2+ concentration on the deposit composition and current effi-
ciency of Co–V electrodeposits
VO2+ (M)
Co (wt.%)
V (wt.%)
CE (%)
0.10
0.135
0.17
0.20
95.4
96.7
95.0
94.8
4.6
3.3
4.3
5.2
32
44
71
59
Fig. 3. Composition of Co–V electrodeposits obtained at various current
densities; pH 6.0, deposit thickness = 1.2 ␮m.
CD: 5 mA/cm2, pH 6.0.

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B.Y. Yoo et al. / Electrochimica Acta 50 (2005) 4335–4343
Table 3
Deposit composition and magnetic properties of Co–V electrodeposits obtained at various current densities
CD (mA/cm2)
Co–V
Co
Co (wt%)
V (wt.%)
CE (%)
Hc (Oe)
Bs (T)
Hc (Oe)
1
3
5
10
25
50
86.0
91.4
95.7
95.9
97.7
98.8
14.0
8.6
4.3
4.1
2.3
1.2
77
76
71
64
34
33
142
118
86
62
13
1.41
1.43
1.52
1.55
1.53
1.51
42
53
58
–
10
43
pH 6.0; deposit thickness = 1.2 ␮m.
indicated in Table 3. Deposits at CD < 10 mA cm−2 are ac-
companied with low hydrogen evolution which increases
with increasing CDs. The magnetic saturation (Bs) increased
and the coercivity (Hc) decreased with decreasing deposit V
contents.
Co–V electrodeposits show a preferred HCP (0 0 2)
orientation, indicating a basal plane parallel to the deposit
surface (Fig. 4a and b). The peak intensity decreases with
increasing deposit V content, a result of decreasing applied
CDs. Deposits (8.6 wt.% V) obtained at 3 mA cm−2, show
a preferred HCP (1 0 0) orientation indicating a basal plane
perpendicular to the surface (Fig. 4c). This change in pre-
ferred orientation is evidently due to the increased deposit V
content, possibly contributing to the deposit magnetic prop-
erties. The grain size (GS) of electrodeposited Co–V with 1.2
and 4.3 wt.% V did not vary significantly: 12–14 nm in the
(0 0 2) plane and 16 nm in the (1 1 0) plane. Co–V deposited
Fig. 4. XRD analysis of Co and Co–V electrodeposits at different cur-
rent densities; pH 6.0: (a) CD = 50 mA/cm2; (b) CD = 5 mA/cm2; (c)
CD = 3 mA/cm2.
Fig. 5. XRD results of binary iron group–V alloy deposits at different tem-
peratures: pH 6.0; CD = 3 mA/cm2.

B.Y. Yoo et al. / Electrochimica Acta 50 (2005) 4335–4343
4339
Fig. 6. SEM of Co (a)–(c) and Co–V (d)–(f) electrodeposits at pH 6.0 and various CDs; (a) and (d): 50 mA/cm2, (b) and (e): 5 mA/cm2, (c) and (f): 3 mA/cm2.
at lower CD (3 mA cm−2) exhibited GS = 41 nm (1 0 0) plane
and 14 nm (1 1 0) plane. Co electrodeposits in the same
CD range also show a preferred HCP (0 0 2) orientation;
no changed orientation at the lower CDs was observed,
however.
The structure of Co–V deposits varies with deposition
from elevated solution temperature (CD = 3 mA cm−2, pH
6.0), resulting in V contents >6 wt%) (Fig. 5a). XRD spec-
tra indicate HCP (1 0 0) and (1 1 0) planes, and HCP (1 0 0),
(1 1 0), (0 0 2) and (1 0 1) planes from solutions at 26 and
50–75 ◦C, respectively, with preferred (1 0 0) orientation. The
peak intensities and broading increased with increasing so-
lution temperature, indicating increased GS.
Thedifferencesinsurfacemorphologyofelectrodeposited
Co and Co–V at various CDs is shown in Fig. 6. The surfaces
of both Co and Co–V are quite similar, smooth with uni-
form distribution of fine nodules when deposited at the higher
CD (50 mA cm−2). Decreasing CD to 5 and 3 mA cm−2 re-
sulted in changes in Co–V alloy surfaces to granular, acicular
(needle-like), dendritic structure with increasing porosity; Co
deposits, however, became increasingly nodular. The chang-
ing morphology of Co–V alloys is apparently a result of in-
creased V incorporated into the Co matrix.
Armyanov [26] showed that generally the easy direction
of magnetization is parallel in the basal c-axis plane for HCP
(0 0 2) Co deposits. Therefore, Co deposits with preferred
(0 0 2) orientation exhibit harder magnetization (higher coer-
civities) than HCP (1 0 0) Co–V deposits which are perpen-
dicular to the basal plane because of crystal anisotropy [26].
Fig. 4 shows that with increasing deposit V content, the (1 0 0)
planeintheCo–Vdepositsbecomesthepreferredorientation,
possibly accounting for the reversal in coercivities shown
in Fig. 7; i.e., Co–V electrodeposits with (1 0 0) planes ex-
hibit harder magnetization behavior than Co electrodeposits;
Hc(Co–V) ∼ 2.8 X > Hc(Co). This change indicates magneti-
zation anisotropy might be stronger than crystal anisotropy in
Co–V electrodeposits. Co electrodeposits at 3 mA cm−2 have
a smoother, slightly nodular surface, whereas Co–V elec-

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B.Y. Yoo et al. / Electrochimica Acta 50 (2005) 4335–4343
Fig. 7. Magnetic hysteresis curves (//) of Co and Co–V electrodeposits; pH
6.0, CD: 3 mA/cm2, deposit thickness = 1.2 ␮m.
Fig. 8. Comparison of magnetic saturation of Co–V alloys by electrodepo-
sition and sputtering at various V deposit contents.
Fig. 8 compares magnetic saturation of electrodeposited
Co–V with RF sputtered Co–V deposits as a function of de-
posit V content [27]. Both exhibit decreasing magnetic satu-
ration with increasing deposit V content.
trodeposits have an acicular, needle-like morphology (Fig. 6)
which results in the shape anisotropy induced by asymme-
try; i.e., it is easier to magnetize the deposit along the long
axis than the short axis of magnetic films perpendicular to
the surface. As indicated in Fig. 7, magnetic saturation of
Co–V deposits with increased V content require stronger ex-
ternal fields. Table 4 shows magnetic saturation of Co de-
posits (1.75T) to be ∼1.23 X greater than Co–V (1.43 T).
The coercivity of the Co–V electrodeposit (∼118 Oe) is ∼3X
greater than the Co deposit (∼42 Oe). The squareness, Br/Bs,
of the hysteresis loops were Co = 0.41 and Co–V = 0.34, re-
spectively.
3.2. Fe–V Electrodeposits
Fig. 9 shows the effects of increasing CD and pH on de-
posit composition. The Fe deposit content increases linearly;
conjointly the deposit V content decreases (Fig. 9a). Increas-
ing solution pH (CD = 3 mA cm−2), however, shows a con-
verging, practically linear trend (Fig. 9b).
Decreasing deposit V content with increasing applied CDs
can be explained by the resulting variations in the partial
CDs. As shown in Table 5, when the applied CD is increased
(pH = 6.0), the partial CDs of V and Fe increased with the
increasing rate for Fe greater than for V; thus, the V content
decreases with increasing CD (Fig. 9a). Similarly, when so-
lution pH is increased (CD = 3mA cm−2), the partial CD of V
deposition remains almost constant, whereas the partial CD
The coercivity of Co–V deposits appears to be a func-
tion of the deposit V content. It decreases with decreased
deposit V content, which in turn, is related to increased CD
(Table 3). Thus, deposits ∼14 wt.% V (CD = 1 mA cm−2) ex-
hibit a coercivity of ∼142 Oe, whereas deposits ∼1.2 wt.% V
(CD = 50 mA cm−2)exhibitacoercivity∼10 Oe. IncreasedV
content increases deposit coercivity probably because vana-
dium being non-magnetic acts to obstruct magnetic wall
movement [23]. Magnetic saturation, Bs, increases with in-
creased CD, from 1.41 to 1.51 T, also as a result of the
concomitantly lowered deposit V and increased Co contents
(Table 3). Coerciviities of cobalt electrodeposited in this CD
range did not vary substantially.
Table 5
Partial current density and current efficiency of Fe–V electrodeposits
iV (mA/cm2)
iFe (mA/cm2)
IH (mA/cm2)
CE (%)
2
itotal (mA/cm2)a
3
5
10
25
50
0.02
0.03
0.04
0.11
0.11
0.41
0.85
1.84
4.14
7.78
2.57
4.12
8.12
20.75
42.11
14
18
19
17
16
Table 4
Effect of vanadium on the magnetic properties of iron group metals
Material
Composition
Hc(Oe)
Bs(T)
pHb
5.5
6.0
6.5
7.0
a
Co
Co–V
Fe
Fe–V
Ni
Ni–V
100Co
91.4Co-8.6V
100Fe
98.5Fe-1.5V
100Ni
99.3Ni-0.7V
42
118
94
27
89
1.75
1.43
2.10
2.05
0.60
-
0.02
0.02
0.02
0.01
0.50
0.41
0.35
0.29
2.48
2.57
2.63
2.70
17
14
12
10
102
pH 6.0.
CD: 3mA/cm2.
CD: 3 mA/cm2; pH 6.0; deposit thickness = 1.2 ␮m.
b

B.Y. Yoo et al. / Electrochimica Acta 50 (2005) 4335–4343
4341
Fig. 10. XRD results of Fe–V and Fe electrodeposits at pH 6.0 and 7.0;
CD = 3 mA/cm2: (a) Fe–V (1.5 wt.% V) and Fe at pH 6.0; (b) Fe–V (2.2 wt.%
V) and Fe at pH 7.0.
creased solution temperature (75 ◦C) resulted in instability of
the solution with precipitation of Fe(OH)2, possibly because
of insufficient citrate concentration.
Nevitt and Aldred [28] calculated the magnetic saturation
of electrodeposited Fe (2.15 T) and Fe–V electrodeposited al-
loys, the latter decreasing almost linearly with increasing V
content. Table 6 shows the experimental values for magnetic
saturation (Bs) of Fe–V electrodeposits from 0.7 to 1.5 wt.%
V (solution pH = 6) are in reasonable agreement with the cal-
culated values. Deposits containing 1.9 and 2.2 wt.% vana-
dium deviated from the calculated values. The differences
might be the result of different deposition conditions; the
latter deposits were electrodeposited at pH 6.5 and pH 7.0,
respectively. At the higher solution pH’s, the deposits prob-
Fig. 9. Composition of Fe–V electrodeposits obtained at various current
densities (a) and solution pH (b).
of Fe decreased (Table 5), resulting in increased deposit V
contents (Fig. 9b).
The CEs of deposits from pH = 6.0 solutions do not change
appreciably(14–19%)withtheappliedCD(Table5). Increas-
ing solution pH (CD=3 mA cm−2) results in decreased CEs,
however (Table 5).
Fig. 10 shows structural changes of Fe–V electrodeposits
as a result of solution pH. The XRD spectra of Fe–V alloys
deposited at pH 6.0 and 7.0 are compared with Fe deposited
at the same experimental conditions. The bcc (1 1 0) plane
was the preferred orientation for both Fe–V and Fe elec-
trodeposits. However, Fe–V deposits exhibit two additional
planes, bcc (2 0 0) and bcc (2 1 1), with weaker intensities.
The addition of V to the Fe matrix is likely the main factor
for the development of the bcc (2 0 0) and (2 1 1) planes. The
intensity of the planes decreased slightly in deposits from
increased solution temperature (50 ◦C) (Fig. 5b). Magnetic
saturation of deposits from 25 ◦C solution was 2.05 T; this de-
creased substantially for the dark, non-metallic deposits from
50 ◦C solutions, because of oxide/hydroxide inclusions. In-
Table 6
Effect of vanadium content on the magnetic saturation of Fe–V
electrodeposits
V content (wt.%)
Bs [28] (T)
Bs (experimental) (T)
pH
0.7
1.1
1.3
1.4
1.4
1.5
1.9
2.2
2.13
2.12
2.11
2.11
2.11
2.11
2.10
2.09
2.21
2.00
2.13
2.05
2.13
2.05
1.88
1.93
6.0
6.0
5.5
6.0
6.0
6.0
6.5
7.0
CD = 3 mA/cm2; deposit thickness = 1.2 ␮m.

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B.Y. Yoo et al. / Electrochimica Acta 50 (2005) 4335–4343
Table 7
posits from solution pH > 7 were non-metallic. Increasing
current density resulted in a decrease in vanadium content
and a sharp increase in H2 evolution (decreased current effi-
ciency).
Effect of pH and CD on deposit composition and coercivity of Ni–V
electrodeposits
Ni (wt.%)
V (wt.%)
CE (%)
Hc // (Oe)
Hc ⊥ (Oe)
pHa
5.5
6.0
6.5
7.0
For Co–V (≥4.3 wt.% V), the preferred orientation
changes from HCP (0 0 2) to HCP (1 0 0). This change in
orientation possibly contributes to the deposit magnetic prop-
erties; e.g., Co–V deposits with (1 0 0) planes exhibit harder
magnetization (higher coercivities) than deposits with (0 0 2)
planes. The GS of deposits containing ꢀ4 wt.% vanadium
did not vary substantially (12–16 nm). Deposits with higher
vanadium content exhibited GS ∼ 41 nm for (1 0 0) planes
and 14 nm for (1 1 0) planes. Both electrodeposited and sput-
tered Co–V deposits exhibit decreased magnetic saturation
with increasing deposit V content.
99.65
99.27
99.63
99.56
0.35
0.73
0.37
0.44
14.3
13.5
10.9
11.5
94
102
110
128
76
69
105
133
CD (mA/cm2)b
3
5
10
50
99.27
99.15
99.37
99.79
0.73
0.85
0.63
0.21
13.5
13.7
10.2
14.2
102
98.4
93.4
115
69
90.8
73.7
141
a
CD = 3 mA/cm2.
pH = 6.0.
b
The Fe–V deposit compositions show similar trends
as Co–V deposits. However, substantially less vanadium
(ꢀ2 wt.%) is incorporated into the deposits. The bcc (1 1 0)
preferred orientation of Fe–V deposits is similar to that
of electrodeposited Fe but with two additional phases, bcc
(2 0 0) and (2 1 1) planes, present.
Magnetic saturation of Fe–V deposits decreases with in-
creased deposit V content. Deposit coercivities increase in
the perpendicular direction, with increasing vanadium con-
tent; however, coercivities do not change significantly in the
parallel direction.
Nickel vanadium deposits contained <1 wt.% V under
similar solution pH and current density ranges. In gen-
eral, the amount of V co-deposited increased as follows:
Ni < Fe ꢀ Co.
ably contained oxide and/or hydroxide contaminants which
reduce magnetic saturation.
The coercivity (Hc) of Fe–V electrodeposits (V contents
0.5–2.25 wt.%) deposited from solutions with pH between
5.5 and 7.0 was measured in the parallel and perpendicular di-
rections. In the parallel direction, the coercivity (Hc = 27 Oe)
was independent of the deposit V content. In the perpendicu-
lar direction, the coercivity increased with increasing deposit
V content.
Comparison of the magnetic properties of electrode-
posited Fe and Fe–1.5V alloy (Table 4) indicates slightly
higher magnetic saturation (Bs) for Fe (2.10 T) than Fe–V
alloy (2.05 T). The coercivity of the Fe deposit (94 Oe) was
higher than the Fe–V deposit (27 Oe).
3.3. Ni–V electrodeposits
Acknowledgment
Because electrodeposited Ni has lower magnetic satura-
tion (0.6 T) than either Co or Fe, a limited exploratory inves-
tigation of electrodeposited Ni–V alloys is presented. Ni–V
deposit compositions and properties as a result of varying
solution pH and CD are shown in Table 7. Under the depo-
sition conditions investigated, the deposit V content was less
than 1 wt.%. The current efficiencies ranged between 10 and
14%. The coercivities of the deposits did not vary greatly as
a result of the minor variations in deposit composition.
The Ni–V electrodeposits show preferred fcc (1 1 1), fcc
(2 0 0) and fcc (2 2 0) planes, the peak intensities increasing in
deposits from increased solution temperatures (Fig. 5c); the
deposit V contents decreased (CD = 3 mA cm−2, pH = 6.0).
Increasing peak intensities with deposition from increased
solution temperatures are indicative of increased GS.
This work was supported by the DARPA MEMS program
(DABT 63-99-1-0020) and the NSF xyz on a chip program.
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