Direct evidence of the low-temperature cluster-glass magnetic state of Nd2/3Ca1/3MnO3 perovskite

Abstract

In the presented study we have revealed a giant exchange bias in a colossal magnetoresistance Nd 2/3 Ca 1/3 MnO 3 perovskite at low temperatures, evident of an intrinsic exchange coupling in this compound. The phenomena found confirms our previous assumption that the low-temperature magnetic structure of the compound is represented by small (nanosized) ferromagnetic clusters immersed within the charge-ordered antiferromagnetic matrix. Magnetic behavior of the Nd 2/3 Ca 1/3 MnO 3 perovskite is consistent with a cluster-glass magnetic state and does not agree with a classical spin-glass state observed in a variety of disordered magnetic systems. We think that the cluster-glass magnetic behavior of Nd 2/3 Ca 1/3 MnO 3 originates from the selforganized phase-separated state of the compound. The Cole-Cole analysis of the dynamic susceptibility at lowtemperatures has shown extremely broad distribution of relaxation times, indicating that spins are frozen at a "macroscopic" time scale. Slow relaxation of the zero-field-cooled magnetization has been experimentally revealed as well. This slow relaxation confirms the cluster-glass magnetic state of the compound. Two strongly different relaxation mechanisms were found: the first one is characteristic for temperatures below the freezing temperature T g ∼ 60 K, the second one is characteristic for higher temperatures. PACS

Exchange bias phenomenon in (Nd1−xYx)2/3Ca1/3MnO3 (x = 0, 0.1) perovskites

“…2,[5][6][7] In the materials which are single-phase at high temperatures but exhibit spontaneous phase separation at low temperatures due to first-order phase transitions, the exchange bias phenomenon has been found relatively recently. Among these compounds, perovskite manganites [8][9][10][11][12][13] and cobaltites [14][15][16][17] should be mentioned. For instance, it was shown that the compound Pr 2/3 Ca 1/3 MnO 3 with spontaneous phase separation consists of an antiferromagnetic matrix with embedded ferromagnetic clusters.…”