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B, [T] B, [T] B, [T]
1 1 Ni Fe 1
Ni 80.5% Fe 19.5% 90% 10% Ni 65% Fe 35%

H, [kA/m] H, [kA/m] H, [kA/m]
−20 −10 0 10 20 −20 −10 0 10 20 −20 −10 0 10 20

−1 −1 −1

FIGURE 20.134 B-H curves for different Ni x% Fe 100−x% permalloy thin films.

The magnetic properties of the Ni 80% Fe 20% (permalloy) thin films are studied, and the field coercivity
(H c ) is a function of the thickness. For example, H c = 650 A/m for 150 nm thickness and H c = 30 A/m
for 600 nm films.
Other Ni 80% Fe 20% (deposited at 25°C) and Ni 50% Fe 50% (deposited at 55°C) electroplating solutions are:

• Ni 80% Fe 20% : NiSO 4 –6H 2 O (200 g/l/), FeSO 4 –7H 2 O (9 g/l), NiCl 2 –6H 2 O (5 g/l), H 3 BO 3 (27 g/l),
saccharine (3 g/l), and pH (2.5–3.5);
• Ni 50% Fe 50% : NiSO 4 –6H 2 O (170 g/l/), FeSO 4 –7H 2 O (80 g/l), NiCl 2 –6H 2 O (138 g/l), H 3 BO 3 (50 g/l),
saccharine (3 g/l), and pH (3.5–4.5).
To electroplate Ni x% Fe 100−x% thin films, various additives and components (available from M&T Chem-
icals and other suppliers) can be used to control the internal stress and ductility of the deposit, keep the
iron content solublized, obtain bright film and leveling of the process, attain the desired surface roughness,
and most importantly to guarantee the desired magnetic properties.
In general, the permalloy thin films have optimal magnetic properties at the following composition:
80.5% of Ni and 19.5% of Fe. For Ni 80.5% Fe 19.5% thin films, the material magnetostriction has zero
crossing. Films with minimal magnetostriction usually have optimal coercivity and permeability prop-
erties, and, in general, the coercivity (depending on the films thickness) is 20 A/m (and higher as the
thickness decreases), and permeability is from 600 to 2000. Varying the composition of Fe and Ni, the
characteristics of the Ni x% Fe 100−x% thin films can be changed. The composition of the Ni x% Fe 100−x% thin
films is controlled by changing the current density, T f /T r ratio (duty cycle), bath temperature (varying
the temperature, the composition of Ni can be varied from 75 to 92%), reverse current (varying the
reverse current in the range 0−1 A, the composition of Ni can be changed from 72 to 90%), air agitation
of the solution, paddle frequency (0.1–1 Hz), forward and reverse pulses waveforms, etc. The B-H
curves for three different Ni x% Fe 100−x% thin films are illustrated in Fig. 20.134. The Ni 80.5% Fe 19.5% thin
films have the saturation flux density 1.2 T, remanence B r = 0.26 T-A/m, and the relative permeability
600–2000.
It must be emphasized that other electroplated permanent magnets (NiFeMo, NiCo, CoNiMnP, and
other) and micromachined polymer magnets exhibit good magnetic properties and can be used as the
alternative solution to the Ni x% Fe 100−x% thin films widely used.
NiFeMo and NiCo Thin Films Electrodeposition
To attain the desired magnetic properties (flux density, coercivity, permeability, etc.) and thickness,
different thin film alloys can be used based upon the microstructure’s and microtransducer’s design,
applications, and operating envelopes (temperature, shocks, radiation, humidity, etc.). As was discussed,
the Ni x% Fe 100−x% thin films can be effectively used, and the desired magnetic properties can be readily
achieved varying the composition of Ni and Fe. For sensors, the designer usually maximizes the flux
density and permeability and minimizes the coercivity. The Ni x% Fe 100−x% thin films have the flux density
up to 1.2 T, coercivity 20 (permalloy) to 500 A/m, and permeability 600–2000 (it was emphasized that

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