Ferromagnetic Ground States with High Transition Temperatures in New Tetragonal Rare-Earth Compounds CeRu2Al2B and PrRu2Al2B

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We report on the discovery of ferromagnetic ground states in the newly synthesized tetragonal compounds CeRu2Al2B and PrRu2Al2B. Polycrystalline samples of these compounds were synthesized and their magnetization M(B) and electrical resistivity \rho(T) were measured as functions of the magnetic field B and the temperature T. CeRu2Al2B is a metallic compound with trivalent Ce ions and is classified into a Kondo-lattice system: a Kondo-like -\ln T dependence of \rho(T) is observed below 32 K. The cusp at T_{\text{N}}{}^{\text{Ce}} = 14.3 K and the steep increase at approximately T_{\text{C}}{}^{\text{Ce}} = 13 K observed in the magnetic susceptibility M/B(T) correspond to antiferromagnetic (AFM) and ferromagnetic (FM) transitions, respectively. T_{\text{C}}{}^{\text{Ce}} is the second highest transition temperature of the Ce-based ferromagnet with no other magnetic elements. PrRu2Al2B is also a metallic compound with trivalent Pr ions. The M/B(T) of PrRu2Al2B shows a cusp at T_{\text{N}}{}^{\text{Pr}} = 26 K and a steep increase at approximately T_{\text{C}}{}^{\text{Pr}} = 11 K, indicating that AFM and FM transitions occur at T_{\text{N}}{}^{\text{Pr}} and T_{\text{C}}{}^{\text{Pr}}, respectively.
2012-04-15