Non-equilibrium collective dynamics of a superspin glass

Superparamagnetism and superspin glass behaviors in multiferroic NiMn‐based magnetic shape memory alloys

“…These equilibrated domains become frozen‐in during further cooling and are retrieved during subsequent heating, indicating that the system shows a memory effect. On the other hand, the evidence that the M ref versus T and M SW versus T curves coalesce at low temperatures (below T w ) and only start to deviate as T w is approached again during heating clearly shows that rejuvenation occurs during the further cooling from T w to 10 K in the stop‐and‐wait protocol because of the chaotic nature of the superspin glass state . The above crucial characteristics of ageing, rejuvenation, and memory effects explicitly corroborate the superspin glass behavior of martensite at T < T P .…”

“…Furthermore, the memory effect, which is known to be an unequivocal signature of superspin glass behavior , was examined by employing the well‐defined stop‐and‐wait protocol . In this protocol, the reference curve was firstly recorded: after the sample was ZFC from 300 to 10 K, a magnetic field of 0.05 T was applied and the magnetization as a function of temperature ( M ref vs. T curve) was measured during heating.…”

Sequence of structural and magnetic transitions in Ni48Co2Mn39Sn11 shape memory alloy

“…To further corroborate the SSG behavior of martensite at ToT P , the memory effect, which is an unequivocal signature of SSG behavior [22,23], was examined using the well defined stop-andwait protocol. In this protocol, the sample was first ZFC from 300 K (above T P ) to the stop-and-wait temperature T w ¼80 K (below T P ), at which the sample was aged for t w ¼14,400 s, before further cooling down to 10 K, and then a magnetic field of 0.05 T was applied at 10 K and the magnetization M SW vs. T curve was recorded during heating.…”

“…These equilibrated domains become frozen-in on further cooling and are retrieved on heating, which indicates that the system shows a memory effect. On the other hand, the evidence that the M ref vs. T and M SW vs. T curves coalesce at low temperatures and only begin to deviate as T w is approached from below clearly shows that rejuvenation occurs as cooling down is continued from T w in the stop-and-wait protocol [22][23][24] because of the chaotic nature of the SSG state. The crucial characteristics of aging, rejuvenation, and memory effects conclusively point to the fact that the martensite shows SSG behavior at ToT P .…”

Spin-glasslike behavior of magnetic ordered state originating from strong interparticle magnetostatic interaction in α-Fe nanoparticle agglomerate

“…The previous studies indicated the appearance of spin-glasslike ordering or ferromagnetic ordering in dipolar-interacting nanoparticle system. 4,5 The spin-glasslike magnetism, observed in some granular film 6 and concentrated ferrofluid, 7 is called superspin glass ͑SSG͒. In addition, some specific granular systems are observed to have ferromagnetic correlation between particle moments.…”