Electron-spin-resonance study of gadolinium borosilicide: A rare-earth ladder compound

Abstract

Electron-spin-resonance (ESR) measurements were utilized as a microscopic probe to gain more information about the magnetic transition in the REB50 compounds. A gadolinium phase (Gd3+=S87∕2) was synthesized and used for this measurement. GdB50 will not form due to the large size of gadolinium, but we have found that with the addition of a small amount of Si, the lattice constants expand and an isotypic borosilicide is formed which can accommodate the gadolinium phase. This phase has a ladderlike arrangement of the gadolinium atoms and although a broad peak in the specific heat has been observed previously at T∼4K, the transition could not be discerned in the susceptibility due to an inevitable low-temperature tail. However, the ESR absorption intensity was found to exhibit a sharp drop at TN=7K, clearly indicating the magnetic transition. The g factor also exhibited a temperature dependence, decreasing rapidly below 30K, indicating the growth of short-range correlation. The temperature dependence of the ESR linewidth was significantly different from that of a three-dimensional antiferromagnetic system, being indicative of the exchange narrowing of a one-dimensional classical spin system. These results indicate that the Gd ions magnetically form pairs along the bond-alternating ladder which is the direction of the second-nearest metal-metal spacing.