|Name||Ms. Judith Roth|
|Organization or Institution||The Florida State University|
Unusual Magnetic Behavior of La0.4Ce0.6Co2P2 Associated with Temperature-Induced Structural Collapse
Kirill Kovnir,a,† Xiaoyan Tan,a,‡ Alexandra Arico,a Alexander A. Yaroslavtsev,c Judith Roth,a Corey M. Thompson,a,# Alexey P. Menushenkov,d V. Ovidiu Garlea,b,* Michael Shatruka,*
a Department of Chemistry and Biochemistry, Florida State University, Tallahassee, FL 32306
A series of rare-earth cobalt phosphides La1–xCexCo2P2 (0 < x < 1) has been comprehensively investigated by structural, spectroscopic, magnetic, and theoretical methods. The drastically different structural and magnetic properties of LaCo2P2 and CeCo2P2, the terminal members of this series, result in unconventional behavior for the intermediate compositions. At the La-rich side of the series (0< x < 0.5) the compounds order ferromagnetically over a long range of temperatures and eventually avail to antiferromagnetic exchange. Compounds studied at the Cer-rich end of the series (6<x<1) order antiferromagnetically. An unusual behavior has been observed for the intermediate composition, La0.4Ce0.6Co2P2. This compound exhibits long-range ferromagnetic ordering at ~230 K, but the structural collapse along the tetragonal c axis results in the abrupt decrease in the total magnetization. While such decrease is usually associated with the ferromagnetic-to-antiferromagnetic, order-order type transition, we find no signature of any antiferromagnetically ordered state below 180 K, as confirmed by neutron scattering experiments. The structural collapse also decreases the bonding interactions between the Co atoms in the [Co2P2] layer while increasing the bonding interaction between the P atoms along the c axis. The unit cell parameters for the high–temperature structure, determined at 298 K, resemble those found for LaCo2P2, while the low-temperature structure, determined at 130 K, appears to be more similar to CeCo2P2. The behavior of this system is currently under further investigation to understand and explain the loss of magnetic ordering upon the collapse of ferromagnetically ordered La0.4Ce0.6Co2P2.