Magnetic properties of Dy3(Co,Ni) compounds at ambient and high pressures

Dy 3 Co, in addition to two antiferromagnetic (AFM) transitions (35 K and T N ∼ 44 K), exhibits a Griffiths-like phase around 65 K and it persists up to ∼ 1 GPa pressure. External pressure alters the magnetic state significantly and results in increase (decrease) of T N (T A F ) by 6.5% ( ∼ 13%) with dT N /dP ∼ 3 K/GPa (dT A F /dP ∼ −4.5 K/GPa). Increase in metamagnetic critical field and other changes with pressure indicate the strengthening of AFM interactions in Dy 3 Co. On the other hand, Dy 3 Ni shows three magnetic transitions at T o ∼ 55 K, T 1 ∼ 39 K (AFM) and T 2 ∼ 24 K (AFM). Experimental evidence points to the magnetic ordering temperature to be at T o ∼ 55 K instead of 39 K as claimed by certain reports. External pressure reduces (increases) the transition temperature T o (T 1 ) by ∼ 7.9% (7.6%) at a rate of −3.5 K/GPa (2.5 K/GPa). Pressure has only marginal effect on the other low temperature transition at T 2 . Additionally, ac-susceptibility data exhibit spin-glass like features, which seem to arise from domain wall movements and probably random freezing of small components of spins, coexisting with dominant long-ranged non-collinear AFM structure in these compounds.