Anomalous compression behavior in lanthanum/cerium-based metallic glass under high pressure

Abstract

In situ high-pressure x-ray diffraction, low-temperature resistivity, and magnetization experiments were performed on a La 32Ce32Al16Ni5Cu15 bulk metallic glass (BMG). A sudden change in compressibility at Ϸ14 GPa and a rapid increase of resistivity at Ϸ12 K were detected, whereas magnetic phase transformation and magnetic field dependence of the low-temperature resistivity do not occur at temperatures down to 4.2 K. An interaction between conduction electrons and the two-level systems is suggested to explain the temperature and field dependences of resistivity of the BMG alloy. Although the cause of the unusual change in compressibility at Ϸ14 GPa is not clear, we believe that it could be linked with the unique electron structure of cerium in the amorphous matrix. An electronic phase transition in BMG alloys, most likely a second-order amorphous-to-amorphous phase transition, is suggested.bulk metallic glass ͉ phase transition R ecent studies of amorphous materials have revealed that more than one distinct amorphous phase can be formed from the same substance, a phenomenon that is called amorphous polymorphism (1-4). The nature of amorphous-toamorphous transition induced by pressure has been a topic of considerable research activity in several substances, e.g., ice, silicon, silica, and carbon (5-13). All these reports have encouraged the search for polymorphic phase transitions in liquids and glasses (14-19). Bulk metallic glasses (BMGs) as a new kind of amorphous material with a maximum size up to Ϸ70 mm in diameter and wide supercooled liquid regions have been fabricated in the last decade (20,21). To the best of our knowledge, evidence for an amorphous-to-amorphous phase transition has rarely been reported in metallic glasses. Very recently, parallel to our work, Sheng et al. (22) reported similar amorphous-toamorphous phase transition in a binary CeAl metallic glass ribbon sample.For decades, both structural and electronic transitions in pure elemental cerium and its crystalline alloys have been intensively investigated. Cerium, which is the first element in the lanthanide series with one 4f electron, has a complex phase diagram. Depending on pressure and temperature, it can be either a paramagnet, an antiferromagnet, or a superconductor. Cerium is also the only pure element to exhibit a solid-solid critical point in the well known ␥ N ␣ isostructural phase transition (23, 24). Many cerium-bearing alloys are heavy-fermion compounds and have anomalous low-temperature resistivity and magnetization behaviors that are relevant to Kondo coupling (25, 26) and also have first-order phase transitions resembling the ␥ N ␣ phase transition for pure cerium or second-order phase transitions above a critical point (27). Recently, a LaCe-based BMG with a maximum size up to 10 mm (28) and a La-based BMG with a maximum size up to 20 mm were developed (29). An interesting question has been raised: Do LaCe-based BMGs have electronic phase transitions similar to pure cerium and its crystalline alloys?In this work, we report...

General 2.5 power law of metallic glasses

“…They are separated by a transition region between ∼2 GPa and ∼5 GPa, indicating a polyamorphic transition in Ce 68 Al 10 Cu 20 Co 2 MG. This phenomenon is similar to those observed in many other rare-earth-elements-based MGs showing kinks of q 1 under pressure (27,28,34,35).…”

Substitutional alloy of Ce and Al

“…Structures and polyamorphic transitions of Ce-Al metallic glasses have recently received increasing attention (18)(19)(20)(21). We studied X-ray diffraction (XRD) of a metallic glass with the Ce 3 Al composition under hydrostatic pressures in helium medium and room temperature (see Materials and Methods for details).…”

High-pressure studies with x-rays using diamond anvil cells

“…Experiments on glassy and amorphous materials have shown that the amorphous-amorphous transition may occur in simple systems; for example, in H2O [407], SiO2 [60], GeO2 [61,204,320], and metallic glasses [215,389]. The ability to induce amorphous materials with pressure, especially those that can be recovered to ambient conditions, provides a way of tuning materials properties that are likely unobtainable using any other method.…”

“…HP XRS allows direct probing of the chemical bonding changes of light elements in noncrystalline materials [267,382]. Relatively speaking, HP XRD remains a primary technique for studying the structural evolution of non-crystalline materials [97,120,198,204,262,264,[383][384][385][386][387][388][389], pressure-induced amorphization or melting [346,[390][391][392][393][394][395][396][397][398][399], and pressure-induced crystallization [58,346,393,397,[400][401][402].…”