Temperature dependent ⁸⁹Y NMR study on multiferroic YCrO₃

Abstract

In this manuscript, we report the 89Y NMR measurement as a function of temperature on single phase and pure polycrystalline YCrO3 sample to study the magnetism and relaxation times on a microscopic level across the magnetic transition (T N ≃ 141 K) from paramagnetic to antiferromagnetic state. The NMR peak width broadens abruptly upon crossing T N due to the onset of internal magnetic fields, while peakshift slight decreases. A slight increase and subsequent anomalous decrease in the NMR peak intensity is observed on approaching T N from 300 K. There is also a significant increase in peak width. The temperature dependence of the 89Y NMR spin–lattice relaxation rates 1/T 1 indicates a phase transition at T N which is of magnetic origin due to Cr3+ ions, with an anomalously rise of fluctuations below T N. Above T N, this spin–lattice relaxation rate can be fitted to a power-law scaling behavior 1/T 1 ∼ T β with an exponent factor β ≈ 0.8, indicates low energy spin fluctuations. Moreover, Knight shift and 1/TT 1 scales linear with the bulk susceptibility which suggests the antiferromagnetic spin fluctuation in the YCrO3 system.

Magnetization reversal, field-induced transitions and H–T phase diagram of Y1−x Ce x CrO3

“…All the samples exhibit standard G-type AFM ordering with substantial increase of the T N from 142 K to 145 K for the compositions x = 0 to 0.2, respectively as estimated from the M-T data. The ordering temperature (141 K) for the pristine compound (YCrO 3 ) is consistent with the previous reports [7,9]. The following eye-catching features are predominant in this system: (i) giant magnitude of the NM in M ZFC branch (∼−127 emu/mol), (ii) large difference in the magnetization (ΔM ∼ 280 emu/mol) between the M FC and M ZFC at low temperature T = 1.9 K and (iii) emergence of spin-reorientation transitions, T SR at low-temperatures below which the strength of the ferromagnetic domains increases due to the incorporation of the Ce at the Y-sites of the sublattice.…”

“…These values are in good agreement with our present Ce doped YCrO 3 system in which R 3+ -Cr 3+ interactions evolved. While the Curie-Weiss temperatures, θ CW lies between −386 K (x = 0) and −664 K (x = 0.2), in-line with the previous reports on pristine compound YCrO 3 as well as Pr substituted YCrO 3 wherein a wide range of θ CW (−325 K to −461 K and −596 K) estimated from the standard magnetization data and by means of NMR Knight shift experiments [9,30,32,[39][40][41][42][43].…”

“…The magnitude of overall magnetization reduces significantly as the concentration of trivalent Ce increases and its contribution is more as compared to the moment of trivalent Cr. Moreover, the intermediate paramagnetic state T IP across 230 K is evident in the semi-log plots of M vs T which is associated with the short-range ordering of trivalent Cr canted spins (figure 4S) consistent with the previous reports [9,26]. FC measurements recorded while cooling and warming cycles under the application of external H DC = 500 Oe (given in the figure 5S).…”

“…These observations are later supported by both dc-magnetization studies and frequency dependence of ac-susceptibility data reported by Yamaguchi et al, and Morishita and Tsushima [14][15][16]. Moreover, very recently Mall and Pramanik reported anomalous spin fluctuations below T N in polycrystalline pristine YCrO 3 compound using the temperature dependent 89 Y nuclear magnetic resonance measurements, which links the WFM and spin-lattice relaxations following the power-law scaling behaviour (T −β ) [9]. Interestingly, the same authors reported a new phase transition (across 230 K) within the disordered intermediate paramagnetic region by means of the temperature dependence of electron spin resonance study [24][25][26].…”

“…The concept of magnetization reversal (MR), negative magnetization (NM) and compensation phenomena (T CMP ) in the rare-earth (R) perovskites R(Cr/Mn)O 3 have swiftly reinvigorated the field of strongly correlated electronic oxides in the recent past [1][2][3][4][5][6]. Among the pool of distorted-orthorhombic (Pbnm) antiferromagnetic (AFM) perovskite family of compounds, yttrium manganite (YMnO 3 ) and yttrium chromite (YCrO 3 ) systems have attracted immense attention because of their fascinating physical properties such as: multiferroic behaviour, exchange-bias, switchable polarization driven by magnetostriction, mixed-phase behaviour (weakferromagnetism, WFM component along the c-axis below AFM ordering) etc [7][8][9]. These compounds attained prominence from the applications point of view since the above intriguing physical phenomena can be readily utilized for the development of many magneto-electronic devices including the read/write heads of hard-drives and spin-valves [10][11][12][13].…”