ELECTRONIC STRUCTURE IN AMORPHOUS AND
CRYSTALLINE NICKEL PHOSPHOBORIDES
THROUGH PHOTOEMISSION, NMR AND
SPECIFIC HEAT
A. Amamou, D. Aliaga-Guerra, P. Panissod, G. Krill, R. Kuentzler
To cite this version:
A. Amamou, D. Aliaga-Guerra, P. Panissod, G. Krill, R. Kuentzler. ELECTRONIC STRUCTURE IN AMORPHOUS AND CRYSTALLINE NICKEL PHOSPHOBORIDES THROUGH
PHOTOEMISSION, NMR AND SPECIFIC HEAT. Journal de Physique Colloques, 1980, 41
(C8), pp.C8-396-C8-399. <10.1051/jphyscol:1980897>. <jpa-00220552>
HAL Id: jpa-00220552
https://hal.archives-ouvertes.fr/jpa-00220552
Submitted on 1 Jan 1980
HAL is a multi-disciplinary open access
archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from
teaching and research institutions in France or
abroad, or from public or private research centers.
L’archive ouverte pluridisciplinaire HAL, est
destinée au dépôt et à la diffusion de documents
scientifiques de niveau recherche, publiés ou non,
émanant des établissements d’enseignement et de
recherche français ou étrangers, des laboratoires
publics ou privés.
ColZoque C8, suppZ6ment au n08, Tome 4 1 , aoGt 1980, page cg-396
JOUKNAL DE PHYSIQUE
ELECTRONIC STRUCTURE I N AMORPHOUS AND C R Y S T A L L I N E N I C K E L PHOSPHOBORIDES THROUGH
FHOTOEMISSION,
NMR AND S P E C I F I C HEAT
A. Amamou, D. Aliaga-Guerra, P. Panissod, G. Krill and R. Kuentzler
L.A.M.S.E.S.
(No 3061, UiniversitQ Louis Pasteur - I n s t i t u t Le BeZ,
4 , rue BZaise Pascal 67070 Strasbourp Ceder, France.
R6sum6.- Nous prdsentons une 6tude des propri6tLs de photo6mission, RYN, chaleur specifique
et aimantation du systPme NiPB dans 1'6tat amorphe et cristallin. Nous proposons un modsle
simple de structure dlectronique interpr6tant ces propridt6s. Les rgsultats de photodmission
sont aussi compar6s 5 ceux obtenus pour les systPmes FePB et CoPB.
Abstract.- We present a study of photoemission, NMR, specific heat and magnetization properties
on the NiPB system in the amorphous and crystalline states. The electronic structure can be
interpreted in a simple model which
explains coherently the various properties. The photoemission results are also compared to those obtained for FePB and CoPB systems.
Introduction :
Several studies have been carried out on the
amorphous Ni?B system. The magnetization properties for concentrations of
-
80 at 2 Ni have been
interpreted by the presence of magnetic clouds in
Co, Ni)PB is also considered.
Experimental procedure :
A~amorphoussample Ni
P B has been prepa78 14 8
a paramagnetic matrix /I/ ; [.MI1 studies /2,3/ ai-
red by the rapid quenching technique. Ni P has
3
been prepdied by sintrying the appropriate consti-
med in particular to the comparison of the quadru-
tuants during 3 days at 900'~ ; then the ingot was
polar parameters on boron with those obtained in
melted in an induction furnace and finally annea-
crystalline Ni B , give conclusive evidence that
3
led during 3 days at 903OC. Ni B has been prepared
the boron atoms in the amorphous structure retain
by sintering the appropriate constituants during
to a significant extent the local symnetry of the
one week at 900°C. The samples have been control-
crystalline counterpart. Specific heat investiga-
led by the X-rays analysis.
tions /4/ show that the electronic specific heat
3
The magnetization properties have been per-
increases noticeably with the nickel concentration.
formed for field up to 52 kOe and temperatures
At our knowledge, little work has been carried
between 4.2 and 300 K ; the investigated tempera-
out on crystalline Ni P and Ni B ; these compounds
3
3
ture range for specific heat measurements was
are characterized by short met,ll-metalloid inter-
1.5 to 6 K. The NMR measurements have been carried
atomic distances which favor covalent bonding.
out by the spin echo technique between 4.2 K and
On another hand, recent photoemission studies
room temperature. The photoemission properties
on amorphous and crystalline CoPB /5/ and FePB 161
(XPS and UPS) have been studied by an ESCA
systems show that the electronic structure can be
(VG Yark 111) ; the XPS azimutal investigation
interpreted in a covalent bonding model. The pre-
did not
sent work is aimed to im~lement the previous
Full details on experimental procedures can be
study on NiPB systems ; the evolution of valence
found elsewhre, respectively ref. 7, 8, 9, 5 .
show the presence of surface effects.
band in transition metal-metalloid systems (Fe,
Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1980897
Experimental results :
However, these values confirm the presence of a
For Ni B and Ni P the magnetization can be
3
3
noticeable d density of states at the Fermi level.
separated into 3 terms /1,10/ : a weak ferromagne-
For Ni78P14B8 the y coefficient /4/ 1.9 mJ/mole K
tic one which is attributed to nickel precipitate ;
is close to that of N i P likely due to the high
3
a verysmall Cyrie-'rleiss type contribution due to
relative concentration of phosphorus in the amor-
magnetic impurities and a temperature independent
phous alloy. The Pauli susceptibilities can be ten-
term related to the matrix susceptibility
x'.
The
-6
experimental X' values are 0.95 10 emu/g for
Ni3B and 0.40
emu/g for Ni P ; these values
3
tatively determined from the
y coefficients ; this
point as well as the Debye temperatures will be
discussed in a further paper.
For W4R, .-the Knight shift and the relaxation
suggest the presence of a non negligible density
and 3 1 in~ Ni B and Ni P
3
3
of states due to nickel d electrons. A previous
rate (TI~)-' for ' I B
study on NiPB amorphous system shows that X' va-
respectively have been determined. The obtained
ries with the alloy composition ; i t has been in-
results can be analyzed in the same way as pre-
terpreted a: the sum of the matrix contribution and
viously /2/ for Ni78P14B8 ; the relaxation rate
of non magnetic impurities contribution.
on the metalloid can be separated in a Korringa
term and a Giovannini-Heeger term. If we neglect
the enhancement effects, the Korringa relaxation
can be interpreted in terms of local susceptibilities on the boron and phosphorus sites. The experimental data suggest that the contribution of s
electrons can be neglected since the Korringa
ratio is much larger than 1. The roughly evaluated
L
Pauli susceptibility xp of the metalloid Pelectrons
are rather low compared to the total susceptibili-
-6
ty ; it is of 0.12 10 emu/g for Ni B and
3
Fig. 1 : Specific heat of crystalline Ni B and
3
Ni P for Ni 78P4B8 see ref. 4
3
.
0.18
emu/g for Ni3P ; the error can reach
0.05
emulg. For Ni
0.12
-6
emu/g on phosphorus and 0.06 10 emu/g
P B the
78 14 8
xpL
is of
on boron 121. These values suggest the presence
The experimental data of the specific heat on
Ni B and Ni P can be described in a classical way :
3
3
3
C = yT + BT (Fig. I).
C includes the terms of
of a low contribution of the metalloid p electrons
to the total density of states at the Fermi level.
About photoemission, let us first remind that
electronic specific heat and of the phonons ; the
for the valence band of pure nickel an abondant
units for C are given in mJ/mole K where a mole
literature has been devoted to the relation ship
is 0.75 Ni + 0.25 B or P. The obtained y values
between the calculated d density of states and
are higher for Ni B (2.80 mJ/mole K) than for
3
the experimental band structure determined by
Ni P (1.44 mJlmole K) but they are appreciably
photoemission /11,12,13/. Our experimental results
lower than that for pure nickel (7.04 mJ/mole K ) .
for pure nickel are in good agreement with those
3
JOURNAL DE PHYSIQUE
C8-398
about 13 eV for Ni B and 16 eV for Ni P and
3
3
Ni78P14B8. These large values can be attributed to
the presence of s-p states due to the metalloid ;
the UPS results will be presented in detail in a
further paper. The lack of well defined photoemitted contribution attributable specifically to
the metalloid s-p states suggests that such states
are spread out over the valence band.
Discussion :
The present study on magnetic specific heat,
NiqR and photoemission properties of amorphous
Ni78P14B8 and crystalline Ni B and N i P can be
3
3
briefly summarized as follows. The properties
Fig. 2 : Valence band spectra obtained with the
A1 Ka radiation in crystalline and amorphous nickel phosphoborides.
of the amorphous alloy are very similar to the
crystalline counterparts ; in particular, the
values of the electronic specific heat, the relaxation rates and the characteristics of the va-
obtained elsewhere 1141. For XPS the electron
lence band are closer to those of Ni P than to
2
distribution curve (EDC) shows a full width at
those of Ni B ; this is likely attributable to
half maximum of 2.7 eV ; the total width of the
3
the higher relative concentration of phosphorus
d band is estimated to 4.5 eV and the total width
in the investigated alloy. The investigated alof the valence band is about I 1 eV ; the maximum
loys are paramagnetic and an appreciable d densi-
A of the EDC referred to the Fermi level is at
ty of states is present at the Fermi level ; the
0.9 eV, a slight shoulder B can be noticed at
evaluated local susceptibilities on phosphorus
about 2.2 eV. These values have been determined
and boron suggest the existence of a low contriin the same way as previously /5,6/.
bution of the metalloid p electrons to the total
For the metal-metalloid compounds, the high
density of states at the Fermi level. The photodensity regions of the EDC's obtained in XPS are
emission results indicate that the d band strucexpected to reflect mainly the structure of the
ture is quite similar to that of pure nickel.
d band /5',6/. The EDC's obtained by XPS on crysTherefore the various properties can be interpretalline Ni B, Ni P and amorphous NiF8P14Bg are
3
3
ted in a model of covalent bonding band structure,
similar to that of pure nickel (Fig. 2). The maxithe upper part being mainly related to d electrons.
mum A is slightly closer to EF (0.7 eV) ; the
In such a model the metal-metalloid bonding inshoulder B is at about 1 . 6 eV for Ni P and
3
duces a vanishing of the exchange splitting and
Ni78P14B8, meanwhile it is at the same energy as
a strong change in the density of states at the
for pure nickel for Ni B. All the FWHM's are
3
Fermi level.
the same as for pure Ni within the experimental
On another hand, studies / 5 , 6 /
on amorphous
accuracy ; the total of the valence band is of
and crystalline FePB and CoPB systems have shown
that a similar model can be applied in order to
interprete the various properties. For the FePB
system, the d band, when compared to that of pure
iron, is strongly modified. For the CoPB system,
the modification is less sensitive ; and the present study shows that in the NiPB system such a
modification is negligible. Therefore it seems
that the filling of the d band of the transition
elements involves an increase of the correlation
between electrons which involves an increasing
stability of the d band.
Acknowledgements :
The authors wish to express their appreciation to Dr M.A. Khan for valuable discussions ;
thanks are also due to Yrs Ravet for her help
concerning the samples preparation and X-ray
References
/I/
Amamou,A. and Durand,J., Communication on Phys.
-I ( 1 9 7 6 ) 191
/ 2 / Aliaga Guerra,D., Panissod,P. and Durand,J.,
Sol. State Comm.
(1978) 7 4 5 .
28
/ 3 / Panissod,p. et al, to be published
/ 4 / Donnelly,T.A., Egami,T. and Onn David,G.,
Phys. Rev. B 0 (1979) 1211.
/ 5 / Amamou,A. and Krill,G., Sol. State C o m .
31 (1979) 971.
-
/ 6 / Amamou,A. and Krill,G., Sol. State Comm.
3 3 (1980) 1387.
/ 7 / Amamou,A. and Sautier,F., J. Phys. F : Yetal
Phys.
(1973) 563.
4
1 8 1 Kuentzler,R., Ph. D. Thesis, Strasbourg ( 1 9 7 0 ) .
/ 9 / Panissod,P., Ph. D. Thesis, Strasbourg ( 1 9 7 6 ) .
/ l o / Amamou,A., Gautier,F. and Loege1,B. : J. Phys
F : Xetal Phys.
(1975) 1342.
5
/ 1 I / Eastman,D .E., 'riir~psel,
F.J . and Knapp. J .A.,
Phys. Rev. Lett.
(1978) 1514.
1 1 2 1 Penn David, R., Phys. Rev. Let.
42
(1979) 921.
/ I 3 1 Feldkamp,L.A. and Davis,L.C., Phys. Rev. Lett.
4 3 (1979) 151.
-
H i f n e ~S. and Wertheim,G.K., Phys. Lett.
%
( 1 9 7 4 ) 349.
/ 1 5 / Ansgar Liebsch, Phys. Rev. L e t t . s ( l 9 7 9 )
1431.