Nuclear Magnetic Resonance and Mössbauer Effect Study of Sn¹¹⁹ in Rare Earth‐Tin Intermetallic Compounds

Abstract

The nuclear magnetic resonance and Mossbauer effect of Sn119 have been studied in the cubic intermetallic compounds RSn, (R = La, Ce, Pr, Nd, Sm, and Yb). Both the isotropic and anisotropic components of the Knight shift were determined in the temperature range 77 to 400 OK. In the cases of l'rSn, and NdSn, in which the shift measurements are proportional to the magnetic susceptibility, the results may be understood in terms of the Ruderman-Kittel-Kasuya-Yosida t,heory, with an exchange interaction, I' ; = -0.2 eV. The cases of CeSn, and SmSn, do not appear to be interpretable in terms of the RKKY theory. For PrSn,, NdSn,, and SmSn, the Miissbarier effect of the Sn119 yielded a resolved quadrupole splitting of approximately 1.1 mm/s, independent of temperature in the range 4.2 to 300 OK. The isomer shift was + 0.70 mm/s, relative t o Mg,Gn, also independent of temperature. The measured quadrupole coupling has been compared with that expected on the basis of the ionic model. No magnetic splitting was ever unambiguously observed, even a t 1.5 OK. Assuming that the magnetic splitting remains masked by the quadrupole interaction leads t o an estimate of H,ff 5 9 x lo3 Oe in PrSn, and NdSn,.Kernresonanzuntemochungen und Untersuchungen des MoDbauereffekts an Sn119 wurden in kubischen, intcrmetallischen Verbindungen RSn, (11 = La, Ce, Pr, Nd, Sm und Yb) untersucht. Es werden sowohl dcr isotrope als auch der anisotrope Anteil des Knight Shift im Temperaturbereich 77 bis 400 O K untersucht. Fur PrSn, und NdSn,, in denen die Verschiebung proportional ziir magnetischen Suszeptibilitat ist, konnen die Ergebnisse im Rahmen der Itudermann-Kittel-Kasuya-Yosida-Theorie verstanden werden, wobei als Bustauschwechselwirkung r = -0,2 eV angenommen wird. Die Falle CRSn, und SmSn, scheinen durch die RKKY-Theorie nicht interpretierbar zu sein. FBr l'rSn,. NdSn, und SmSn, ergibt der MoObauereffekt von Sn1l9 eine anfgeloste Quadrupolaufspaltung von ungefahr 1,l mm/s unabhangig von der Teinperatur im .Bereich 4,2 bis 300 OK. Die isomere Verschiebung betragt = 0,70 mm/s, relativ zu Mg,Sn. ebenfalls unabhangig von der Temperatur. Die gemessene Quadrupolkopplung wird mit der a u s dem Ionenmodell erwarteten verglichen. Magnetische Aufspaltung wurde unzweideutig nicht beobachtet, sogar nicht bei 1,5 OK. Unter der Annahme, da13 dic Magnetaufspalt,ung diirch Quadrupolwechselwirkung vcrdeckt bleibt, wird Heff 5 9 x lo3 C)e in PrSn, rind NdSn, abgeschstzt. Introduct,ionIt is well known that whenever an atom or ion possessing a permanent magnetic moment (e.g., a rare-earth ion) is immersed in a metallic matrix, an oscillatory unpaired spin density will be induced in the conduction electron distribution, l ) Work was performed in the Ames Laboratory of the Atomic Energy Commission.Contribution No. 1984.

Nuclear magnetic resonance hyperfine fields in the hexagonal laves phase compounds ScMn₂, ErMn₂, and TmMn

“…There Is a substantial temperature independent Knight shift in ErMn^ and TmMng and no temperature dependence of the Knight shift. This Is strikingly different from the case of the rare earth 1ntermetal11c compounds with Sn (36,37), Al (38,39), P, As, Sb, and BI (10), all those that have been studied heretofore. This Is also different from the case of the beryllium-based Laves phase intermetallic compounds, (40), and V^X compounds investigated by Clogston and Jaccarino (41) and discussed by Bennett e_t a]_.…”

Samarium in Crystal Fields, a Case of Strong J‐Mixing

“…The Knight shifts Kf(T) a t the nonmagnetic site in both SmAL, 12, 231 and SmSn, [13,24] have been observed to be anomalous in the sense that the curvature of the temperature dependence as well as the sign at low temperatures are reversed as compared to the free-ion behaviour, and that the cross-over is suppressed (see Fig. 5, as compared to Pig.…”

Relevance of knight shift measurements to the electronic density of states

“…For example, Jones [206] has tabulated the nonmagnetic site , Knight shift results of rare earth intermetallic compounds in terms of cf. The same results [205,[218][219][220][221][222][223][224][225][226][227][228][229][230] are plotted in a different form in figure 31, namely in terms of ~ == H' errlH~~. Atomic hype rfine behavior is thus normalized out, providing a crude estimate, in J1-B, of the spin moment residing at a nonmagnetic site due to the local moment disturbance.…”