Evidence of a cluster spin-glass state in B-site disordered perovskite SrTi0.5Mn0.5O3

Abstract

SrTi0.5Mn0.5O3 (STMO) is a chemically disordered perovskite having random distribution of Ti and Mn over 1b site. Striking discrepancies about the structural and magnetic properties of STMO demands detailed analysis which is addressed. To explore the magnetic ground state of STMO, static and dynamic magnetic properties were studied over a broad temperature range (2-300 K). The dc, ac magnetization show a cusp like peak at Tf ~ 14 K, which exhibits field and frequency dependence. The thermoremanent magnetization is characterized by using stretched exponential function and characteristic time suggests the existence of spin clusters. Also the other features observed in magnetic memory effect, muon spin resonance/rotation and neutron powder diffraction confirm the existence of cluster spin glass state in STMO, rather than the long range ordered ground state. Intriguingly, the observed spin relaxation can be attributed to the dilute magnetism due to non-magnetic doping at Mn-site and competing antiferromagnetic and ferromagnetic interactions resulting from the site disorder. I. IntroductionCompeting magnetic interactions added to chemical disorder can hinder long range magnetic ordering and may lead to frozen spin states at low temperatures. The key point of present work is to understand such effect of chemical disorder on magnetic ground state of B-site of double perovskite SrTi0.5Mn0.5O3 (STMO). Meanwhile, another important factor which is found to promote the spin-glass (SG) state in double perovskites is geometrical frustration arising from the tetrahedral topology 1,2,3 of the magnetic ion. Here, the term double perovskite has been specifically used for B-site ordered systems having the general formula A2BB'O6. In these systems, geometrical frustration does not always lead to the short range ordered state but can instead produce some more exotic magnetic ground states including spin-ice, spin-liquid etc. 4,5,6 , in addition to long range order. Intriguingly, for B-site ordered double perovskites having magnetic cation at B'-site,

Cluster Spin Glass Formation in the Double Double Perovskite CaMnFeTaO6

“…3a). A 50% reduction of Tf over the same field change was observed in BaBi0.28Co0.72O2.2, 20 and a 36% suppression was reported for the cation disordered perovskite cluster spin glass SrMn0.5Ti0.5O3 (Sr2MnTiO6) as field increased from 0.01 to 1 T. 21 Slow relaxation dynamics in CaMnFeTaO6 are evidenced by the changes of slope seen in the AC susceptibility data of Fig. 5 at 20 and 30 K, where the cooling rate was changed by a factor of two, but were not explored more systematically.…”

Emergence of low-temperature glassy dynamics in Ru substituted non-magnetic insulator CaHfO3

“…The value of β is independent of Ru concentration. Also, the obtained values of β ∼ 0.5, is close to the values reported in other CG compounds like Zn 3 V 3 O 8 , Nd 5 Ge 3 , Cr 0.5 Ga 0.5 Ga, and insulating magnetic glass compounds SrTi 0.5 Mn 0.5 O 3 , Sr 2−x La x CoNbO 6 [18,[63][64][65]. The non-zero value of β at 20 K (above T f ) suggests the presence of short-range interactions among magnetic entities even above the T f .…”

“…Both the bifurcation temperature between ZFC -FC curves (T irr ) and peak temperature (T f ) of ZFC curve reduces on increasing the applied magnetic field. Such kind of features has been reported in unconventional SG systems [18,[49][50]. For a conventional SG, it is noted, T irr ≤ T f , and below this temperature, FC curve becomes independent of temperature [51].…”

“…The observed magnetism in these systems has been mostly explained by Ruderman-Kittel-Kasuya-Yosida (RKKY) interactions among magnetic cations via conduction electrons. Some of these materials, along with their insulating nature, also show glassy magnetic phases at low temperatures [17,18]. Initially, spin glass (SG)/cluster glass (CG) dynamics had been anticipated in metallic alloys due to RKKY interactions [19].…”