HAL Id: jpa-00214492
https://hal.archives-ouvertes.fr/jpa-00214492
Submitted on 1 Jan 1971
HAL is a multi-disciplinary open access archive for the deposit and dissemination of sci- entific research documents, whether they are pub- lished 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.
SUSCEPTIBILITY AND RESISTIVITY OF ζ -PHASE ZINC-TRANSITION METAL COMPOUNDS
A. Caplin, J. Dunlop, R. Taylor
To cite this version:
A. Caplin, J. Dunlop, R. Taylor. SUSCEPTIBILITY AND RESISTIVITY OF ζ-PHASE ZINC- TRANSITION METAL COMPOUNDS. Journal de Physique Colloques, 1971, 32 (C1), pp.C1-209- C1-210. �10.1051/jphyscol:1971165�. �jpa-00214492�
JOURNAL DE PHYSIQUE Colloque C 1, supplkment a u no 2-3, Tome 32, Fkvrier-Mars 1971, page C 1
-
209SU SCEPTIBILITY AND RESISTIVITY
OF [-PHASE ZINC-TRANSITION METAL COMPOUNDS
A. D. CAPLIN, J. B. DUNLOP and R. H. TAYLOR Physics Department, Imperial College, London S. W. 7. England
Rksumk. - Les phases des compos6s ZnlsMn, Znl3Fe et Znl ~ C O sont bien ordonnees. La distance entre les ions de transition est
-
5 A. L'ion Mn porte un moment magnetique alors que les ions Fe et Co n'en portent pas comme dans les solutions correspondantes dans Zn. En dessous de 20 OK, ZnlsMn s'ordonne et est faiblement ferromagnbtique.On observe un fort signal en R. P. E. et le facteur g passe de la valeur 2,O a 200 OK a la valeur 3,O en dessous de 4O K.
A basse temperature la resistivite de ZnlsFe et Zn I 3Co varie consid6rablement avec la temperature, indiquant un phkno- m6ne de diffusion des electrons.
Abstract. - The c-phase compounds Znl3Mn, Zn13Fe and Zn13Co are crystallographically well-ordered with
-
5 A between transitional ions. Mn carries a moment but Fe and Co do not, just as in the corresponding dilute solid solutions in Zn. Below 20 OK Zn13Mn orders and is weakly ferromagnetic ; a strong e.p.r. signal is observable and the g-factor increases from 2.0 at 200 OK to 3.0 below 4 OK. There is strong temperature-dependence of the resistivities of Znl ,Fe and Znl SCO at low temperatures, indicative of electron-electron scattering.H kG
FIG. 2.
-
Magnetization curve of a T-Mn sample at 4.2 OK.The dilute transitional impurity dissolved in a free- dent (Fig. 1) ; the i-Fe samples show considerable varia- electron-like solvent, and the pure transition metal bility, but are distinctly more paramagnetic than itself, represent two limiting cases in the theory of S-Co, whose susceptibility is about equal to that of magnetism. An intermediate situation which, by pure Zn (- 0.1 x loe6 emu/g).
combining the localized nature of the former problem The room temperature resistivities of these com- with the periodicity of the latter, should prove ame- pounds are high : about 90, 30 and 20 pQcm for nable to understanding, is provided by the ordered [-Mn, [-Fe and [-Co respectively, but our samples C-phase compounds Zn,,X, where X can be Mn, had quite good resistance ratios, generally between Fe or Co. Brown [I] has shown that in these materials 10 and 30. Their resistivities are strongly temperature- the transition ions are well-separated (-- 5 h;) and dependent a t low temperatures (Fig. 4) ; that of each is surrounded by a slightly distorted sphere of [-Mn is very exactly proportional to T ~but with ~ ~ ,
zinc atoms. some additional term near the magnetic transition.
The high temperature susceptibility of i-Mn fits The temperature dependence of 5-Fe and 5-Co is a Curie-Weiss law (Fig. 1) with p,, = 1.82 p,, between T Z and T ~ . The magnetoresistance of S-Mn 8 = 36 OK and
X,
= 0.53 x lod6 emu/g. It orders is large and negative, and peaks a t a temperature ferromagnetically at about 20 OK (deduced from a close to that of the magnetic transition (Fig. 2).plot of HIM versus M~ 121) with a saturation moment
Fig. 1. - Magnetic susceptibilities of the 5-phase Mn, Fe and Co compounds ; note the ten-fold scale expansion below the axis for 5-Co. The Curie-Weiss plot for the GMn
data is a best fit to the points above 150 OK.
Erratum : The symbols for Co alloys and the symbols for Fe alloys have been inadvertently interchanged in the figure.
-0.4 0.2 n -0
)CB'*
0.2 70.4
of only 0.3 p~ per Mn ion (Fig. 2). Our e. p. r. expe- riments (at X-band on powder samples) show a strong signal below 200 OK, with g = 2.0 down to 150 OK,
and an increasing positive g-shift a t lower tempera- -b- tures (Fig. 3) ; no correction for demagnetizing fields
has been made, for at most it would account for 20
%
0of the observed shift. The susceptibilities of i-Fe and I-Co are small and almost temperature-indepen-
r I 7
Our contention that in the compound tbe magnetic state of each ion is determined by the local environ- ment is supported by the close correlation of magnetic properties with the corresponding dilute solution in zinc : in solution Mn, Fe and Co are respectively magnetic, on the borderline, and nonmagnetic 131;
even the irreproducibility of S-Fe is mirrored by tbe sen- sitivity of the dilute solution to sample treatment [4], It therefore seems reasonable t o think of the tran- sition ion in the compound as forming a virtual bound
I ~ ~ ~ ~ I ~ ~ ~ I I ~ ~ ~
-;=M";; [ . . m m - = * = :
- -
-
.=I
- -- 2 - . .
. . '
-r
1
Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1971165
C 1 - 2 1 0 A. D. CAPLIN, J. B. DUNLOP AND R. H. TAYLOR
state (v. b. s.), with the implication that s-d hybridi- zation, and not d-d overlap, is the important inter- action. The increased paramagnetism of c-Fe with respect to 5-Co, which corresponds to an additional density of states of
-
10 stateslev per Fe, may be attributable to exchange enchancement of the v. b. s.as the magnetic regime is approached. The extraor- dinarily large g-skift and small saturation moment of [-Mn are more dificult to understand.
FIG. 3. - Magnetization, magnetoresistance, e.p.r. g-value and e.p.r. line width of the [-Mn compound as a function of tem- perature. The indicated transition temperature Tc is that deter-
mined from an Arrott plot [2].
If these materials were not ordered the resistivity would be large at all temperatures, about 110, 105 and 50 pRcm respectively [5] ; at T = 0 tke resistivity of a perfectly ordered sample vanishes because, to think in virtual bound state terms, the strong scatte- ring at each transitional ion is repeated from unit cell to unit cell and is therefore non-dissipative. The T312 behaviour of 5-Mn no doubt represents scattering by spin excitations ; the temperature-dependence of the resistivityof 5-Fe and 5-Co is too large and too slow to be a phonon term, and it is more likely that it corres-
ponds to the onset of incoherent scattering : at finite temperatures the occupancy of the v. b. s. fluctuates, consequently the scattering phase shift is no longer quite the same in every unit cell, and a finite resis- tivity appears. This description is essentially equiva- lent to that of electron-electron scattering in a pure
FIG. 4. - Temperature-dependent part of the resistivity for the (-phase Mn, Fe and Co compounds. The resistivity of pure
Zn is also shown for purposes of comparison.
transition metal, but in a situation in which it would be inappropriate to speak of a d band.
We would like to thank Dr H. E. N. Stone for his invaluable metallurgical advice and assistance. This work has been performed during the tenure of S. R. C . studentships by two of us (J. B. D. and R. H. T.), and with S. R. C. financial support.
References
[I] BROWN (P. J.), Acta Cryst., 1962, 15, 608. [4] CAPLIN (A. D.), Physics Letters, 1967, 26, 46.
[2] ARROTT (A.), Phys. Rev., 1957, 108, 1394. [5] BOATO (G.), BUGO (M.) and RIZZUTO (C.), Nuovo [3] VAN DEN BERG (G. J.), LOW Temp. Phys. - LT9 (Part B), Cimento, 1966, 45, 226.
1965, 955. Plenum Press.
