Field-induced orbital order-disorder transition in anA-type antiferromagnetic manganite: High-field study ofNd0.45Sr0.55

Abstract

Magnetization and magnetoresistance were measured in A-type antiferromagnet Nd 0.45 Sr 0.55 MnO 3 utilizing pulsed magnetic fields up to 45 T. We have observed a ferromagnetic transition accompanied by a discontinuous decrease of resistivity. The temperature dependence of the resistivity in the ferromagnetic state showed characteristics of a three-dimensional metal. The observed phenomena are explained in terms of simultaneous destruction of the d x 2 Ϫy 2 orbital ordering and the A-type antiferromagnetic spin ordering by magnetic field.

Reduction of critical field for magnetic and orbital-ordering phase transition in impurity-substituted Nd0.45Sr0.55MnO3 crystal

“…15,18 The resistivity shows a small jump at T N , being barely metallic below and above T N . These results are consistent with previous reports, 15,17 where the anisotropic transport properties and the magnetic-field-induced phenomena of Nd 0.45 Sr 0.55 MnO 3 have been already reported in more detail. Five percent substitution of Cr for Mn drastically reduces the T N by ∼50 K; instead the underlying FM state replaces the A-AFM state in the temperature range of 170-200 K (see also Fig.…”

“…15 This A-AFM phase competes with the FM metallic phase so that application of magnetic fields induces the transition from the A-AFM phase to the FM metallic one (i.e., the 2D FM phase to the 3D FM one). 17 However, the A-AFM order is robust against magnetic fields; in Nd 0.45 Sr 0.55 MnO 3 , the 2D FM to 3D FM transition occurs at μ 0 H = 35 T. In this study, we demonstrate that the robustness of the A-AFM phase with the orbital-order can be controlled through impurity doping method, leading to a novel gigantic magnetoresistive effect.…”

“…The data of the parent compound Nd 0.45 Sr 0.55 MnO 3 (y = 0) are also included for comparison. 17 The phase boundary between the A-AFM and FM orders is determined by the isothermal magnetoresistance measurements, which is also consistent with the thermal ones. As seen from the phase diagram, the critical field for the AFM to FM phase transition becomes larger with decreasing temperature in both y = 0 and 0.05 whereas the critical field of y = 0.05 is much smaller than that of y = 0.…”

Field-induced abrupt change in magnetization of the manganite compounds(LaR)0.45(CaSr)0.55Rana1, Kuberkar2, Malik3 2006Phys. Rev. B373250View full textAdd to dashboardCite

“…[1][2][3] At half-doping, the charge-ordered and AFM state in certain compositions, like La 0.5 Ca 0.5 MnO 3 , Pr 0.5 Sr 0.5 MnO 3 , etc., is susceptible to external factors such as temperature, magnetic field, pressure, etc. [3][4][5][6][7][8][9] Further, when x varies between 0.5 and 1, different kinds of AFM spin arrangements manifest. As x increases in this region, the A-type of layered AFM spin arrangement and orbital ordered states appear which are not susceptible to moderate external factors.…”

“…2 The temperature and magnetic field induced magnetic phase transitions in manganites also depend upon factors such as: ͑i͒ A geometrical index called the tolerance factor ͑defined as t = ͕͗r A ͘ + r O ͖ / ͱ 2͕r B + r O ͖͒, ͑ii͒ the size-disorder at the A-site ͑quantified as 2 = ⌺x i r i 2 -͗r A ͘ 2 ͒, and ͑iii͒ the impurity doping at the Mn-site. [1][2][3]10 Some Pr-based half-doped and hole-doped compounds possess a smaller tolerance factor and, therefore, their charge and orbital ordered ͑CO and OO͒ AFM state [7][8][9][11][12][13][14][15][16] is rather stable as compared to those of having a larger tolerance factor. The study of magnetic field induced phase transitions in such CO and OO Pr-based systems has recently become the focus of research in manganites because of the following special features.…”