Specific heat and magnetocaloric effect of the S=1/2 spin-ladder compound (CH$_{3})_{2}$CHNH$_{3}$CuCl$_{3}$

(CH$_{3})_{2}$CHNH$_{3}$CuCl$_{3 }$is the best laboratory model for the S=1/2 spin ladder comprising ferromagnetic rungs and antiferromagnetic legs [1]. We have determined the magnetic phase diagram of this compound in fields up to 18 T by means of specific-heat and magnetocaloric-effect measurements for two crystal orientations, with either the so-called $B$ or $C$ plane perpendicular to the field direction. For both orientations, we find power-law dependences of the critical field of the long-range antiferromagnetic order on temperature, behavior indicative of the Bose-Einstein condensation of spin triplets due to the cancellation of the energy gap by the magnetic field. [1] T. Masuda \textit{et al}., Phy. Rev. Lett. \textbf{96, }047210 (2006).