Magnetization of an electroless deposited nickel-phosphorus alloy

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Magnetization of an electroless deposited nickel-phosphorus alloy

J. Fléchon, S. Karbal, F. Machizaud, E. Du Trémolet de Lacheisserie

To cite this version:

J. Fléchon, S. Karbal, F. Machizaud, E. Du Trémolet de Lacheisserie. Magnetization of an electroless deposited nickel-phosphorus alloy. Journal de Physique, 1985, 46 (8), pp.1405-1409.

�10.1051/jphys:019850046080140500�. �jpa-00210084�

Magnetization ^of

^an

electroless deposited nickel-phosphorus alloy

J. Fléchon, ^S. Karbal, ^{F. Machizaud}

Laboratoire de Physique ^des Dépôts Métalliques, Université Nancy I, B.P. 239, ⁵⁴⁵⁰⁶ Vandoeuvre-Lès-Nancy Cedex, ^France

and E. du Trémolet de Lacheisserie

Laboratoire Louis Néel, CNRS-USMG, 166X, 38042 Grenoble Cedex, ^France

(Reçu ^{le 19 décembre 1984, révisé le} 15 février ^1985, accepté ^{le 28 mars} 1985)

Résumé. ²⁰¹⁴ On étudie l’influence de différents recuits sur l’aimantation d’un alliage partiellement ^désordonné Ni91P9. ^{Le moment} magnétique

03C3*o,o

^{et la} température ^{de Curie} Tc varient linéairement avec la température ^de recuit, Ta, jusqu’à Ta ^{= 523 K et le} comportement ^reste celui d’un faible ferromagnétique. Lorsque Ta ^devient égale ^ou supérieure ^{à 573} K, ^il apparait ^{sur les} diagrammes de rayons X la raie (200) ^{du nickel c.f.c. et l’on observe}

une brusque augmentation ^de

03C3*o,o

^{et de Tc. Ces résultats sont en accord avec une étude}

thermomagnétique

^ancienne qui montrait que ^cet alliage ^se transforme en un mélange cristallin de nickel _pur et de phosphure ^{de nickel} Ni3P après ^un recuit à 773 K. Nous avons confirmé l’existence à basse température d’une anomalie dans la variation

thermique de l’aimantation.

Abstract. ²⁰¹⁴ The influence of various annealings ^{on the} magnetization ^{of a} partially disordered Ni91P9 alloy ^has

been investigated. ^The magnetic ^moment

03C3*o,o

and the Curie temperature Tc ^{are found to} vary linearly ^{with the} annealing temperature Ta up ^to Ta ^{= 523 K and the} alloy ^{behaves like a weak} ferromagnet. ^With Ta > 573 K, the (200) reflexion of the f.c.c. nickel appears in the X-ray patterns ^{and a} sharp increase in Tc ^and

03C3*o,o

^{is observed.}

These results agree with previous thermomagnetic data which showed the alloy ^{to be} completely crystallized ^{in a}

mixture of _pure nickel and Ni3P alloy ^after heating ^to Ta ^{= 773 K.} Anomalous thermal variation of the magnetiza-

tion is observed below 50 K, ^as previously ^observed by other researchers.

Classification Physics ^Abstracts

75.30

1. Introduction.

The

magnetic properties

^{of nickel}

phosphides

^have

been

already

^{studied for a} long ^{time : as}

early

^as 1960, ^a

thermomagnetic study

^of disordered

Ni1-xP x alloys

^{has been}

performed by

^{one of us}

[1].

^In 1967,

IBM

laboratories

investigated

^both

crystalline Ni3P

found to be a Pauli paramagnet [2] ^and

amorphous Ni1-xP x alloys [3].

^{More recent works on these}

alloys [4-6]

^were extended in a

thorough

paper

[7]

devoted to the concentration _range

0.15

^x

0.25.

Last, ^some anomalies were

pointed

^{out in the thermal}

variation of the

magnetization

of electroless

deposited amorphous

^NiP

alloys

[8].

Recently

^a structural model for

amorphous Ni1-xP x alloys

^was

proposed,

^{with a} local order

varying

^with

increasing

^x

[9]. Starting

^{from a} f.c.c.-like structure at lower x values, ^{it was} shown that for ^x >

0.15,

a

hexagonal ordering

^of

pseudo-dodecahedra

gra-

dually changes

^{into a} continuous random

packing

of relaxed dodecahedra

[10].

^The f.c.c.-like structure

was

actually

^observed

by

EXAFS studies on electro-

deposited

^NiP

alloys [11].

^{As most of the}

magnetic

studies have been

performed

^with

alloys containing

more than 15 at.

% phosphorus,

^we decided here to

study

^{a low P content}

alloy, namely Ni91 P9.

^The

preparation

^{and main}

properties

of this electroless

deposited alloy

^are

presented

^{in a recent} paper

[12],

where the influence of

annealing

^on

physical

pro-

perties

^is

emphasized.

2.

Experiments.

The

powders

^{have been}

prepared by

^the

liquid phase

oxidoreduction

technique usually employed

^{in our}

laboratory [1].

^After

being carefully

^{washed and dried,}

they

^{have been}

analysed

^{with an} accuracy within a

few percent

by

^{means of an}

absorption spectrophoto-

meter. Last,

they

have been annealed

during

^{5 hours}

in a vacuum of 10-6 torr at various temperatures

Ta :

seven

samples,

^labelled

hereafter

1 to 7, ^{have been} annealed;

sample

¹ five hours at

Ta

^{= 323 K ;}

sample

²

Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphys:019850046080140500

1406

five hours at 323 K and then five hours at

Ta

^{= 373 K ;}

sample

^{3 three}

annealings during

five hours at 323 K, 373 K and

Ta

^{= 423 K, and so on... up to}

Ta

^{= 623 K}

for sample ^7.

Both

magnetic

and structural

properties

^{of these}

five samples ^were

investigated

^{in order to correlate}

their evolution ^with

Ta :

- the

magnetic

^moments

Q(H, T)

^{were measured}

by

^an extraction method from 4.2 to 300 K in a super- conductive coil _up to 6 tesla ;

- the X-ray

analyses

^were

performed

^{in an auto-}

matic CGR 060 diffractometer.

3.

Magnetic properties.

Illustrative Arrott

plots

^{are drawn in}

figure

^{1 for the}

two

samples

^with

Ta

^{= 523 K} and 323 K : since the

H/y

scale has been

magnified

^{in order to}

give

^a

drawing

^{as clear as}

possible,

^the

high

^{field data for}

Ta

^{= 323 K do not appear but their}

extrapolation

down to zero

(HI u)

^is

given by

dotted lines. The

slopes

^{of these} asymptotes ^{remain constant from} 80 to 300 K, but increase

markedly

^{below 80 K for}

every

sample.

. Fig. 1. ^- Isothermal

u,T(H/ u)

plots ^{for two annealed} amorphous Ni91 P 9 alloys. Open circles, T a = 323 K ;

closed circles, Ta = ^{523 K.}

The

experimental

^results

concerning

^the

samples

¹

to 5 are summarized in

figure

2, ^where

(a*, T)’

^is

^plotted

against ^the

squared

temperature. ^{The Curie} tempe-

rature is deduced from linear

extrapolation

^above

room temperature ^{of our}

experimental

^{data. At low} temperature, ^{below 50} K, an excess

magnetization

appears which cannot be

expected

^{in a weak homo-}

geneous ferromagnet :

assuming

this anomalous effect to be

parasitic (we

shall discuss it in a further

section),

^{we define}

Jg o

^{as the}

extrapolation

^down

to 0 K of the linear parts ^{of the}

U*2 (T 2) plots.

^We

note that

sample

² (with

Ta

^{= 373}

K)

^{does not differ}

markedly

^from

sample

^1.

This behaviour is not

surprising

because the struc- tural states stabilized at 323 and 373 K are very similar : differential thermal

analysis experiments

have shown that the first exothermal

phenomena

observable when

heating

^these

alloys

appear

only

near 420 K. The same is true for the temperature coefficient of the electrical

resistivity,

^that

begins

to increase at this same temperature

[14].

We

give

ⁱⁿ

figure

3 the variations of

T c

^and

Qo,o

as functions of the

annealing

temperature

Ta.

^{It has}

been

pointed

^out

previously [1]

that those

samples,

Fig. ^{2. - Thermal} dependences ^of

C1, T’

^{defined as the inter-}

section of the dotted lines with the H / C1 ^{= 0 axis in} figure ^1.

The curves labelled 1, 2, 3, 4, ^{5 were} observed with samples

annealed at Ta ⁼ 323, 373, 423, 473, ⁵²³ K, respectively.

when annealed at 773 K, ^became

crystalline powders consisting

^of pure nickel and

Ni3P phosphide.

^Since

Ni3P

^{is not}

ferromagnetic [2],

^these

crystalline powders

should exhibit the Curie temperature

Tc

^{= 631 K}

of _pure nickel, ^{and a}

magnetic

^{moment that can be}

simply

^{derived as} 0.67 times that of _pure nickbl

(UNi

^{= 58.4 emu} g-

1),

^i.e. _{co, 0} ^{= 39 emu}

g - 1.

(Indeed

in

Ni9 I Pg,

^{we find 4.96 wt}

^%

^P, hence 33.17 wt

% Ni3P

and 66.83 wt

%

^{Ni after}

annealing.)

So, ^{we have} also

plotted

ⁱⁿ

figure

^{3 those}

calculated

values

(squares)

for

T c

^and

Qo,o

^at

Ta

^{= 773 K, which are}

aligned

with our

experimental

^results

(circles). Experimental

values for

T, and a*,o

^at

Ta

^{= 773 K have been}

measured for various nickel

phosphides [1],

^{and those}

concerning

^the

alloy

^{with 5 wt}

%

^{P are}

given

ⁱⁿ

figure

³

(triangles) :

^the agreement with the calculated values is correct.

Last, for

samples

^{6 and} 7,

quite

^a different behaviour is observed :

a(H,

T) is saturated

beyond

^{10 k0e}

and a small

high

^field

susceptibility

remains viz.

a-’ OulOH - 0.15 x 10-6 Oe-’

^{above 80 K and}

0.25 x 10-6 Oe-1 at 4.2 K, that is ^one order

of magni-

tude smaller than for samples ^{1 to 5. The}

a*,o

^values

given

^{in the}

figure

^{3 for}

Ta

^{= 573 K and 623 K are}

simply

the saturation

magnetic

^moment

( a 0,0

^#

30 emu

g-’).

^For

Tc

^{it was no}

longer possible

^to

derive an

extrapolated

^Curie temperature ^{form the} Q2 ⁼

f«(J2) plot,

^{where 0 =}

TIT ,

^{since the}

magnetic

moment deviates from

the.Jl - (J2

^law

^(weak

^ferro-

magnet)

and varies rather as the moment of the

crystalline

nickel, ^i.e.

as.J (1 - ^{(J2) (1}

⁺

^{8 )}

^{to within}

a few percent

[15].

So, ^{we measured}

directly Tc

^for

these two

samples by

^{means of a} balance in a

magnetic

field of 500 Oe and found

T,, - ,

^{621 K, i.e. a value}

close to that of _pure nickel (631

K);

^{these data are}

given

^{also in}

figure

^3.

Fig. ^{3. -} Dependence ^{on the} annealing temperature ^{of the} Curie temperature Tc (closed symbols) ^{and of}

a*,O,

^which

is defined by extrapolating ^{to T2 = 0 the linear} part ^of the

(QO,T)2

^{= f(T2) curves in figure 2} (open symbols)

for samples ^{1 to} 5, and is the saturation magnetization

for samples 6 and 7. Circles : our present ^data. Squares : calculated values for a crystalline mixing ^{of 66:8 wt} % ^Ni

and 33.2 wt % Ni3P, ^i.e. (Ni91 P 9). Triangles : ^observed

values for Ta ^{= 773} K, from reference [1].

4. Structural

properties.

The structural state of ^an

as-prepared sample

^is

given by

^the X-ray

diagram given

ⁱⁿ

figure

4. The material appears ^to be

partially

disordered : the nickel reflexions exist except ^the

(200)

one, but are broadened.

The nearest

neighbours

^between

(111) planes

^are

observed from R.D.F.

[14],

^but

3.60 A. away

^instead

of 3.56 A in the f.c.c. structure of nickel. This disorder

might

^{arise, in the} above-cited structural model

[9],

from the

regions

where the local order is

pseudoico-

saedral : these ones induce stresses in the

neighbouring regions

with f.c.c. structure, which extend over wide

zones for this metalloid concentration.

Figure

⁵ illustrates the noticeable structural modi- fications due to a thermal treatment at 573 K : the

(200)

^{reflexion is observed and was}

already

percep- tible with

Ta

^{= 523 K.}

Last, ^{after an}

annealing

^{at 723} K, ^{we can observe} in

figure

⁶

sharper

lines which indicate the existence of

only

^{two well}

crystallized phases, namely

pure nickel and

Ni3P.

5. Discussion.

Below 50 K, ^{we also observe a} large

magnetization deviating

^{from the linear}

relationship

^between

(UO,T )2

Fig. ^{4. -} Diffraction curve giving ^the intensity ^{as a function}

of the angle 0, ^{1 =} f (0), ^{at room} temperature (CuKa radiation) ^{for an} as-prepared sample.

1408

Fig. ^{5. 2013 7 =} f (0) ^{for a} sample ^{annealed at 573 K.}

and T2 in

figure

^{2. The same effect seems to occur}

in an

amorphous electro-deposited Ni84P,6 alloy,

as can be seen in the inset of

figure

^{2 taken from}

reference

[7],

^{where a}

sharp

increase of a2 is observed below 0.3

T,,

^{i.e. about 50 K} also. A similar

problem

was raised

recently by

^Iida [8], who observed an ano-

malous

concavity

^{of the}

(1(T)

^{curves in}

amorphous

nickel

phosphides : unfortunately

^his

study

^{was limited}

to above 77 K, ^and

only

^the

phosphorus

^richer

alloys

did exhibit this

anomaly

^{above this} temperature.

By

decreasing

^the

phosphorus

content, this

anomaly

was shifted towards lower temperatures ^{and could}

no

longer

be observed. Our measurements,

together

with those of Berrada et al.

[7],

have shown that this anomalous effect exists also in the nickel-rich chemical

nickel-phosphorus alloys.

^{We note that this low} temperature

anomaly

^{does not}

disappear,

^{even after}

further

annealings

^{at 573 K and 623 K}

(samples

⁶

and

7), although

^{it is reduced about}

by

^{a factor 2.}

This anomalous contribution is also associated with

a marked increase of the

high

^field

susceptibility (see § 3).

Above 50 K, ^the

samples

^{labelled 1 to 5 behave}

as weak

homogeneous

ferromagnets except ^{at low}

magnetic

^{fields as in the case of} nickel-rich Ni-Y

amorphous alloys [13].

The values of

Tr

^and

yo (circles

ⁱⁿ

Fig. 3)

^{are seen to} vary

linearly

^with

Ta

Fig. ^{6. - I =} f (9) ^{for a} sample ^{annealed at 723 K.}

up ^to 523 K and

extrapolate

^for

Ta

^{= 773 K to the}

values 631 K and 39 emu

g-’ expected

^for

crystal-

line

alloy

of initial

composition Ni91 P 9 (squared symbols).

On the other hand,

T c jumps

^{from 463 K}

(sample 5)

to 621 K

(sample 6) and a*,o

from 21.5 (5) ^to

30 emu

g-l (6)

^{after an}

annealing

^at

Ta

^{= 573 K.}

Moreover,

sample

^{6 no}

longer

^{behaves as a weak}

ferromagnet.

These drastic

changes

^{are associated}

with the appearance of the

(200)

^{reflexion in the} X-ray

diagram (Fig. 5). Sample

^{7 does not differ}

markedly

from sample 6, ^{and the observed values of}

T, and a*

for these

samples

^{are close to} the values

given

ⁱⁿ

[1]

for the

fully crystalline alloy

^{that was obtained}

by annealing

up ^to 773 K

(triangled symbols).

In conclusion, ^this

study

^{indicates that a} strong correlation exists between the evolution of the local order and that of the

magnetic

parameters

(magne-

tization and Curie

temperature)

^{in the disordered}

Ni9,Pg alloys; magnetic

^{anomalies are observed}

below

80

^K,

^namely

^an increase of the

magnetization

and of the

high

^field

susceptibility : they

^{can be}

related with the fact that co,o ⁼

30

^emu

^g-l

^{when the}

structural

changes

^occur

(Ta

> 600

K),

^{instead of}

39 emu

g-l

^as

expected

^{for a}

mixing

^of

crystalline Ni3P

^{+ Ni. The}

missing

^{nickel is}

perhaps

^involved

in

heterogeneous regions exhibiting

^a

composition

Ni,,P

^(x > 3). ^{Due to a} different structural order,

these

regions

^{could order at low} temperature. ^Unfor-

tunately,

^{no data is}

presently

^available expect ^for

Ni3P,

^{known to be a Pauli} paramagnet.

Acknowledgments.

We thank MM. A. Barlet and M. Maeder for the

magnetization

^{and Curie} measurements.

References

[1] FLECHON, J., Thesis, Nancy (1960).

[2] GAMBINO, ^R. J., MCGUIRE, ^T. R., NAKAMURA, Y.,

J. Appl. Phys. 38, ³ (1967) ^1253-5.

[3] ALBERT, ^P. A., KOVAC, Z., LILIENTHAL, ^H. R., MCGUIRE, ^T. R., NAKAMURA, Y., ^J. Appl. Phys.

38,

³ (1967) ^1258-9.

[4] SIMPSON, ^A. W., BRAMBLEY, ^D. R., Phys. Status Solidi b 49 (1972) ^685-91.

[5] PAN, D., TURNBULL, D., J. Appl. Phys. ⁴⁵ (1974)

1406-12.

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[8] IIDA, K., ^J. Magn. Magn. ^{Mater. 35} (1983) ^226-8.

[9] MACHIZAUD, F., KUHNAST, ^F. A., FLECHON, J., ^Conf.

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[10] MACHIZAUD, F., KUHNAST, ^F. A., FLECHON, J., ^J.

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[11] OKAMOTO, T., FUKUSHIMA, Y., ^J. Non-Cryst. ^Solids 61-62, ¹ (1984) ^379-84.

[12 ] FLECHON, J., KARBAL, S., MBEMBA, G., submitted for

publication in Mater. Chem. Phys. (Elsevier).

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[14] MACHIZAUD, F., Thesis, Nancy (1973).

[15] DU TREMOLET DE LACHEISSERIE, E., ROUCHY, J., ^J.

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