Evolution of magnetic phase transition in intermetallic borocarbide Pr 1− xDy xCo 2B 2C

Abstract

The recently reported magnetic phase diagram ( T N versus de Gennes factor deG) of the body-centered tetragonal RCo 2B 2C series indicates that compounds with R=Pr orders at a higher temperature ( T N≈10.2 K) than that of the isomorphs R=Nd ( T N=3.0 K), Er ( T N=4.0 K), Sm ( T N=6.0 K), Ho ( T N=5.4 K), Dy ( T N=7.8 K) (Rapp, El Massalami, Phys. Rev. B 60 (1999) 3355; El Massalami et al., Phys. Rev. B, submitted). Since the deG of the latter compounds are higher than that of Pr compound, then such non-monotonic evolution of T N with deG deserves further investigations. In that direction, we synthesized and investigated the magnetic phase diagram of the series Pr 1− x Dy x Co 2B 2C ( x=0.0, 0.09, 0.13, 0.345, 0.797, 1.0) wherein deG spans the interval from 0.8 ( x=0) to 7.0819 ( x=1). The obtained unit-cell parameters are in excellent agreement with the Vegard's law, demonstrating that the Pr and Dy atoms substitute each other randomly. Magnetic measurements reveal that the saturated magnetic moment (at 2 K and 90 kOe) increases linearly with x ( ∂μ/ ∂x≈4.7(5) μ B). Furthermore, for x<0.17, T N( x) decreases sharply with x ( ∂T N/ ∂x≈−36(1) K), while for x⩾ 0.17, T N( x) increases as ∂T N/ ∂x≈5.8(1) K. The overall evolution of T N with deG reproduces satisfactorily the behavior of the above cited RCo 2B 2C compounds. These results will be discussed in terms of the hybridization between the 4f and the conduction electrons.