PARAMAGNETIC RESONANCE SPECTRA OF 4d AND 5d TRANSITION ELEMENTS

HAL Id: jpa-00214369

https://hal.archives-ouvertes.fr/jpa-00214369

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.

PARAMAGNETIC RESONANCE SPECTRA OF 4d AND 5d TRANSITION ELEMENTS

W. Low, S. Maniv

To cite this version:

W. Low, S. Maniv. PARAMAGNETIC RESONANCE SPECTRA OF 4d AND 5d TRAN- SITION ELEMENTS. Journal de Physique Colloques, 1971, 32 (C1), pp.C1-937-C1-938.

�10.1051/jphyscol:19711335�. �jpa-00214369�

CHAMP CRIS TALLIN : IMPURETES PARAMAGNETIOUES ET EFFETS DE PAIRES

PARAMAGNETIC RESONANCE SPECTRA OF 4d AND 5d TRANSITION ELEMENTS

W. LOW and S. MANIV

Microwave Division, Department of Physics, The Hebrew University of Jerusalem, Israel

Rhumb. - Le spectre de resonance paramagnetique de Nb4+, Ws+, Mo3+ dans un champ axial. celui de CszZrCla, est prksente. Le spectre de Tc4+ et Re4f dans le champ cubique de KzPtC16, Cs2ZrCla et (NH4)2PtC16 a etk mcsurk de manikre detaillk. Le spectre de I'Ctat ^{T U} est decrit soigneusement puis compare B la theorie.

Abstract. - The paramagnetic resonance spectra of NbJ*, Ws+, Mo3+ in axial field, in CslZrCl6, are reported.

Theyspectrum of Tc4t and Red+ in the cubic field in K2PtC16, Cs2ZrCln and (NH4)2PtClb was measured in detail. The spectrum of fs state was carefully plotted out and compared with theory.

We briefly report measurements on the 4d and 5d transition elements in the crystal field of Cs2ZrC16.

Among the elements that were studied in detail are Nb4+ and W S C , Mo3+, TcJf and Re4+. Some of these elements were studied in similar crystal fields such as K2PtCI, and (NH,)IPtCI,, as well as Cs,HfC16.

The ions

NU'+

and W5' have similar electronic structure, 4d1 and 5d1 respectively. Their spectra were studied in the crystal field of Cs,ZrCl,. Both spectra can be explained to arise from thc paramagnetic ion taking the place of the Zr4+ ion. However, the spec- trum consists of the superposition of three spectra corresponding to three ions per unit cell, with a tetra- gonal distortion along the cubic axes.

The spectra can be described by the spin Hamil- tonian :

with parameters :

The spectrum of Nb4+ shows a number of strange aspects. First of all, one would expect a cubic field rather than a tetragonal field if Nb4+ were to take the place of Zr4+. Secondly, it is found that g ! ! < g,.

There is at present no definitive explanation of this spectrum.

The spectrum of W5

',

on the other hand, is similar to Mo5+ in K,SnC16 [I], and shows g l l > g,, A

>

B, as expected. In princ~ple, from the measured values of g:I, g,, A and B, one should obtain values for the crystal field parameters

A/&

where 1 is the spin orbit coupling, 6 the tetragonal splitting, and for K the core polarization factor and P = 2 ,Jl%/r3. However, some of these parameters are highly sensitive to small changes in the measured values. The calculated values of the tetragonal field is very much larger than can be reasonably expected.

It is at present not clear what the mechanism of the charge compensation is. An interstitial CI- ion in the adjacent cell may possibly be the origin. ENDOR measurements may elucidate this point in more detail.

The spectrum of Molybden can probably be accoun- ted for by a tetragonal spectrum with S = 312 and three ions per unit cell.

The parameters in the spin Hamiltonian are :

The small deviation of gll from the pure spin value is consistent with a very large octahedral crystal field splitting.

The electron configuration of ions such as ~ e ~ + , Tc4+ and Cr3". are nd3 where n = 5,4, 3, respectively.

From symmetry consideration we can deduce that one of the electron states of d 3 + in the strong cubic crystal field is

r,

state. If that state is ground state, the spin Hamiltonian and the E. P. R. spectra must in principle show an angular dependence 121.

Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:19711335

C 1

-

⁹³⁸ W. LOW AND S. MANIV

~e =

g p [ ~ j " ~ ' f i + ~ ' f ] H'," - st)

^,(I)

o l +

Where the s:),"' I:"') and H;"", are the n-th components of the irreducible operators of order m, constructed

+ A

²

$s?)]

from the vector operators S, I and H [3].

In the case of Cr3+ and V 2 + , J A ( + I U ( , Ig

I

^%

I

^u

I

and the angular dependence is very small

(I

2

s?' + A

²

,$

^S"

] ⁺ f

SL~)] [4]. In the case of Re4+ and Tc4+,

1

A

I

>

I

⁽ⁱ 1, Ig

I

>

/

u 1, and the angular dependence is more pro-

$1) ](I) (1) ~ ( l )

-

~ ( 1 ) ~ ( l )

1 - 1

+

s-1 1 o o minent [2].

(3) The spectrum of Tc4+ in K,PtC16 was studied in detail. The angular dependence was determined and the relative intensities of the lines were measured. The following parameters were found :

A comparison between the parameters of the

I',

Hamiltonian for Re4+ (5d3), Tc4+ (4d3), and Cr3+ (3 d3) for octahedral symmetry

Host and ion T ^(OK) g u/g U/A Ref.

- - - -

-

-

K2PtC16 : Re4+

...

1.815

+

^{0.001 (- 7.2}

+

^{0.5) x (- 9.8}

+

^0.3) x lo-'

c)

K2PtC16 : T C ~ " 4.2 1.989 1

+

^{0.000 5}

^-

^{1.0 x (- 8.9}

-

^{0.1) lo-3 (b)}

MgO : Cr3+ 290 1.980 3

+

^{0.000 5}

-

⁰

-

⁰

^("1

C)

R. 0. RAHN and P. B. DORAIN, J. Chem. Phys., 41, 10 (1964) ; 41, 3249 (1964).

(b) This work.

ii

W.-LO< Phys. Rev., 101, 1827 (1956), and also other data (to be published).

References

[ l ] Low (W.), Phys. Letters, 1967, 24 A, 46. [3] FANO (U.) and RACAH (G.), Irreducible Tensorial

[2] MAW (S.), BRONSTEIN (J.) and Low (W.), Phys. Sets, Academic Press Inc., N. Y., 1959.

Rev., 1969. 187, 403. [4] To be published.