Bulk and Local Susceptibility of RB12 (R - Ho, Er, Tm)

High precision measurements of magnetoresistance Delta rho/rho=f(T,H) and magnetization M(T,H) have been carried out on single crystals of rare earth dodecaborides RB12 (R - Ho, Er, Tm) at temperatures 1.8-30 K in magnetic fields up to 70 kOe. The high accuracy measurements allowed us to analyze quantitatively a behavior of derivative d(Delta rho/rho)/dH=f(T,H) and magnetic susceptibility chi(T,H)=dM/dH in paramagnetic and magnetically ordered phases of dodecaborides under investigation. It was shown that negative magnetoresistance anomalies observed in present study in paramagnetic state of RB12 (R - Ho, Er, Tm) can be consistently interpreted in frameworks of a simple relation between resistivity and magnetization - Delta rho/rho similar to M-2 proposed by K. Yosida. A local magnetic susceptibility chi(loc)(T,H)=(1/H(d(Delta rho/rho)/dH))(1/2) was deduced directly from the magnetoresistance measurements and compared with bulk susceptibility chi(T,H)=dM/dH results of the present study. Moreover, the susceptibility dependences chi(loc)(T,H) and chi(T,H) have been applied to analyze in detail the H-T magnetic phase diagram of RB12 (R - Ho, Er, Tm).