Study of ferromagnetic correlations caused by impurities in nonmagnetic materials by the method of small-angle scattering of polarized neutrons

The possibility of the study of ferromagnetic correlations caused by $d$-metal impurities in nonmagnetic matrices is discussed. The polarization and magnetic-nuclear interference obtained by analyzing the small-angle scattering of polarized neutrons in a CuZn(20) alloy with Ni impurity ($1$ at $\%$) are reported. It has been shown that Ni is clustered in the CuZn matrix with the characteristic correlation radius in the range $100<R_c<5000\,$Ådepending on the thermal processing of the samples. The cross correlation function determining magnetic-nuclear interference is satisfactorily approximated by the exponential $\exp(-r/R_c)$, where r is the distance. It has been found that the nonmagnetic matrix CuZn(20) with an almost uniform distribution of $1\%$ Ni impurity has metamagnetic properties in the field $H\approx0.5\,$T at room temperature.