Thermal relaxation of field-induced irreversible ferromagnetic phase in Pr-doped manganites

Abstract

We have investigated the magnetic and transport properties of Pr 0.65 Ca 0.35 MnO 3 and Pr 0.82 Na 0.18 MnO 3 with almost same doping level under various magnetic fields. Upon applying a field of 4 T, both compounds undergo a metamagnetic transition from antiferromagnetic (AFM) to ferromagnetic (FM) in the low temperature region. The field-induced FM state is very stable for at least 10 5 s even after removing the field. This irreversible FM behavior is different from the spontaneous FM ordering as well as the FM state in a reversible metamagnetic transition. We discuss this unusual FM phenomenon found in the Pr-doped manganites with the AFM ground state in terms of the reorientation of Mn spins pinned by localized Pr moments.

First order magneto-structural transition in functional magnetic materials: phase-coexistence and metastability

“…M-H curve obtained by subsequent field cycling between ± H max , where H max >> H M . A very similar behaviour has now been observed in CMR Mn-oxides (Dho and Hur 2003) and magnetocaloric materials (Chattopadhyay et al 2004;Tang et al 2004).…”

Effects of the grain boundary on the coercivity of barium ferrite BaFe12O19

“…We also grew single crystal of barium ferrite using a floating zone method. Details on the growth conditions were described in the previous paper [22,23]. To make a sample with grain boundaries, we crushed single crystals, which were then finely grounded, pelletized, and sintered at 1000 1C for 20 h. All sintered samples were cut into two pieces.…”

Metamagnetic phase transitions induced by static and pulsed fields in (Sm0.5Gd0.5)0.55Sr0.45MnO3 ceramics

“…4, at temperatures below 60 K, the shape of the magnetization isotherms M(H) obtained in pulsed magnetic fields almost completely coincides with the magnetization curves measured in static magnetic fields at 4.2 K. The metamagnetic phase transition to an ordered ferromagnetic state occurs in a critical magnetic field equal to H c1 ≅ 25 kOe, which remains constant with an increase in the temperature to 60 K. The stability of the induced ferromagnetic phase at temperatures in the range from 4.2 to 60 K is also indi cated by the temperature dependence of the magnetic susceptibility χ(T) measured during heating of the sample, in which the ferromagnetic phase was induced by a strong magnetic field at a temperature of 18 K. The temperature dependence of the magnetic suscep tibility corresponds to the phase transition from an ordered ferromagnetic state to a disordered paramag netic state with an increase in the temperature to a critical value T c ≈ 48 K. The temperature equal to 60 K corresponds to the complete destruction of the long range ferromagnetic ordering of manganese spins and can be regarded as the boundary of stability of the induced ferromagnetic phase, which substantially exceeds the region of the existence of the metastable antiferromagnetic state in zero magnetic field. It should be noted that the magnetization isotherms measured in the temperature range 4.2-60 K do not contain significant discontinuities that are character istic of the previously studied irreversible metamag netic phase transitions [21][22][23][24][25][26] induced in both the static and pulsed magnetic fields. Therefore, the mechanisms proposed in the aforementioned works for the irreversible stabilization of the magnetic field induced ferromagnetic phase cannot explain the pre sented experimental results.…”