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Solid State Magnets
Study of Magnetostructural Correlations in ThCr2Si2-Type Phases

This research is supported by the National Science Foundation CAREER Award (DMR-0955353)

Figure 1. Crystal structure of RCo2P2. The planar square nets of Co atoms are highlighted with gray.

 


Figure 2.
Temperature dependence of magnetic susceptibilities of La1-xPrxCo2P2.

The central focus of this project is on the magnetic and structural properties of rare-earth cobalt phosphides with the ThCr2Si2-type structure (Fig. 1). While ternary phosphides RCo2P2 (R = La, Ce, Pr, Nd, Sm) show rather simple magnetic behavior,1 quaternary phases La1-xPrxCo2P2 exhibit multiple magnetic transitions, leading to the observation of such interesting phenomena as metamagnetism and magnetic pole reversal.2,3 The ferromagnetic transition temperature of LaCo2P2 (TC = 132 K) is dramatically raised upon substitution of R for La, reaching almost room temperature for La0.12Pr0.88Co2P2 and La0.25Nd0.75Co2P2 (Fig. 2). This is in drastic contrast to the isostructural La1-xRxMn2E2 (E = Si, Ge) phases,4 in which the ferromagnetic transition remains essentially unaffected by the substitutions in the rare-earth sublattice.

The increase in the ferromagnetic ordering temperature can be rationalized by the analysis of the calculated spin-polarized density of states, which reveals a larger difference in the population of the majority and minority spin subbands for the higher R content.2 This leads to stronger intralayer exchange interactions between the Co centers. The observed magnetic and structural properties prompt investigation of the rare-earth cobalt phosphides under high applied pressure and/or magnetic field, which might lead to detection of new magnetic and/or structural transitions. The exact nature of the observed magnetic ordering will be probed with neutron diffraction and XMCD, experiments that are currently underway.

References:

  1. Reehuis, M.; Jeitschko, W. J. Phys. Chem. Solids 1990, 51, 961-968.

  2. Kovnir, K.; Thompson, C. M.; Zhou, H. D.; Wiebe, C. R.; Shatruk, M. Chem. Mater. 2010, 22, 1704-1713.

  3. Thompson, C. M.; Arico, A.A.; Kovnir, K; Shatruk, M. J. Appl. Phys. 2010, 107, 09E316/1-3.

  4. Duman, E.; Acet, M.; Dincer, I.; Elmali, A.; Elerman, Y. J. Magn. Magn. Mater. 2007, 309, 40-53.

 
 
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Last updated 09/16/2010