Theory of the Susceptibility of CeB6

Abstract

Cerium hexaboride is an antiferromagnetic metal with a Néel temperature of 3°K. The high-temperature inverse susceptibility of this material is observed to decrease with decreasing temperature more rapidly than would be expected from a Curie-Weiss law. Since the temperature at which this deviation appears is much higher than the eventual ordering temperature, short-range ordering effects should be negligible. Also, it can be shown that crystal-field effects alone cannot produce such a decrease in χ−1. In this paper we offer a possible mechanism which explains this behavior. Basically, we assume that the Ce–Ce exchange arises through an indirect exchange involving the conduction electrons. We visualize the conduction electrons as moving in the spaces between the boron complexes so that the magnitude of the s-f exchange will be different for the different crystal-field states of cerium. In a cubic field the 2F5/2 state of Ce3+ splits into a Γ7 and a Γ8. Low-temperature measurements of the saturation moment indicate that the Γ7 state lies lowest. Therefore, as the temperature decreases, the Γ8 state, which protrudes into the space between the borons and, hence, contributes strongly to the s-f exchange, is frozen out, leaving only the weakly coupled Γ7 state.

Multipolar phases and magnetically hidden order: review of the heavy-fermion compound Ce1−xLaxB6

“…The goal of this review is to draw a coherent picture from the myriad of investigations which have been done into CeB 6 and its doped derivatives such as Ce 1−x La x B 6 since its original synthesis in 1932 [1]. Following its discovery, much attention was paid to its potential as a cathode material [2], with some early interest in the following decades regarding its physical behaviour [3][4][5][6] before modern condensed matter physics became interested in its magnetic ordering phenomena.…”

Magnetic properties of CeB6, PrB6, EuB6, and GdB6

“…Cross section view of the cryogcuic lraradoy lialance. Legend: 1) Eleutroriic balance vacuum jar, 2) sample ~I ' C C Y S port, 3) glass-to-metal O-ring seal, 4) elcctrieal conilcetor, 5 ) safrty valve, 6) vacuum chamber, 7) magnet pole cap, 8 ) tare weight pan, 9) liquid helium bayonet connector; 10) helium pumping port, 11) deaar cvacurtion valve, 12 The susccptibilities of the light rare earth hexaborides, with the exception of SmB,, can be reasonably described by Curie-Weiss laws with effective moments close to the Hund freeion values. I n the case of SmB,, the susceptibility has unusual behavior that has been attributed by Ment,h et al [5] and Cohen et, al.…”

Revealing the Nature of Antiferroquadrupolar Ordering in Cerium Hexaboride: CeB6

“…36 Initially Ce 3+ multiplet 4f 1 was thought to be split by the crystalline electric field into a Γ 7 ground state with a Γ 8 excited state. 38 However, this was later reversed to the Γ 8 quartet ground state, which is four-fold degenerate with 2-orbital and 2-spin degrees of freedom, located 46 meV below the Γ 7 doublet state. 23,39,40 Our present results give ∼62 meV separation between Γ 7 and Γ 8 , reflecting experimentally findings.…”