Nuclear magnetic relaxation study of the establishment of order in the ammonium halides

Sharp, A. R.; Pintar, M. M.

doi:10.1016/0301-0104(76)80074-2

Cited by 19 publications

(4 citation statements)

References 29 publications

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“…The ammonium halides are known for their ability to be supercooled and superheated by large temperature ranges. ,,,,− This explains the large hysteretic regions observed in the warming and cooling χ( T ) curves. From these curves, the increase at T β‑δ_Cl = 135 K in χ( T ) (Figure ) was due to the β phase of NH 4 Cl remaining supercooled all the way down to 135 K before transitioning into the δ phase.…”

Section: Discussionmentioning

confidence: 99%

Magnetic Ordering of Ammonium Cations in NH₄I, NH₄Br, and NH₄Cl

Meng

Gao

2019

J. Phys. Chem. C

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Different types of magnetism arise mainly from how electrons move and interact with each other. In this work, we show how protons (H+) also exhibit magnetic behavior. We measured the magnetic susceptibility of the ammonium halides and identified pronounced increases at 232, 233, and 243 K for NH4I, NH4Br, and NH4Cl, respectively, all of which coincide with the geometric ordering of their ammonium cations. With extensive literature establishing the fact that the ammonium cations exhibit rotational motion even toward the lowest temperatures, we take into account that the orbital motion of the protons carries a magnetic moment and find it to be larger than that of the paired electrons. Consequently, the structural phase transitions are magnetically driven as the system attempts to lift 8-fold energy degeneracies of the proton orbitals via Jahn–Teller distortions. Our findings identify that NH4 + cations are capable of comprising magnetism which appears to be ubiquitous in ammonia-based molecular solids.

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Section: Discussionmentioning

confidence: 99%

Magnetic Ordering of Ammonium Cations in NH₄I, NH₄Br, and NH₄Cl

Meng

Gao

2019

J. Phys. Chem. C

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“…In most crystals a single TI minimum was observed as in simple ammonium halides [6], (NH,),SeO, [7], (NH,),Ce(NO,), [7], (NH,),SnCI, [7], (NHJReO, [8], NaNH,SeO, . 2 H,O [9], and NH,HSO, [lo].…”

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confidence: 96%

Rotational Motion of the Ammonium Ions in (NH₄)₃H(SeO₄)₂ Studied by NMR

Tritt‐Goc

Piślewski

Hoffmann

et al. 1993

Physica Status Solidi (b)

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Triammonium hydrogen diselenate, (NH,),H(SeO,),, undergoes a sequence of successive phase transitions: phase I (trigonal R3m) T,, = 332 K, phase I1 (trigonal R3) T,, = 302 K, phase I11 (triclinic P1) Tc3 = 275 K, phase IV (monoclinic) Tc4 = 181 K, and phase V (monoclinic) [l, 41. In the high temperature phases I and I1 the crystal exhibits a superionic conductivity of protonic type. The low temperature phase V is ferroelectric, whereas ferroelastic properties were found in phase 111. It was suggested that the phase transitions are related to order or disorder of SeOi-or NH: ions but the mechanisms for the transitions are still not recognized. Our interest in this particular system has been stimulated by recent cw and pulse EPR experiments performed in our laboratory. Thc purpose of these investigations is to examine the dynamical properties of NH; groups and to see which role, if any, they play in the phase transitions observed in this material.The spin-lattice relaxation times Tl have been measured with a SXP-4/100 Bruker pulse spcctrometer at 90 MHz within the temperature range 100 to 345 K. The temperatures were stabilized with an accuracy of f l K using a nitrogen gas flow unit and a minimum of 20 min was allowed for a sample to reach temperature equilibrium. The relaxation time T,was measured with the magnetization recovery method n -z -7c/2 on a polycrystalline sample. The time between the pulse sequence (the repetition time) was taken to be eight to ten times Tl. The recovery of magnetization was found to be exponential within the experimental error over the entire temperature range studied. The relaxation times exhibit two discontinuities in their temperature dependences (Fig. 1) at 302 and 275 K, respectively, due to the phase transitions of first-order character, consistent with the crystallographic work [ I , 21. The other two phase transitions in the triammonium hydrogen diselenate at 332 and 181 K, respectively, show a less distinct nature and are not pronounced in TI. I n the temperature region below 200 K we observe well resolved double minima due to two chcmically inequivalent ammonium ions NH: (1) and NH: (2). The ions form hydrogen bonds with the oxygen atoms. The NH: (1) ions appear to form the three stronger hydrogen bonds with Ro-H...o = 0.181, 0.194, and 0.198 nm whereas the N H l ( 2 ) ions are involved in two weaker hydrogen bonds with lengths of 0.255 and 0.211 nm, respectively. There are also differences in the average N-H bond lengths which are 0.100 and 0.078 nm for NH; ( I ) and NH,f (2), respectively. The ratio of the number of NH; (1) ions to N H l (2) in the crystal unit cell is equal to 2: 1.' ) Smoluchowskiego 17, PL-60-179 Poznan, Poland.

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“…As shown in Fig. 1a, the NH4 + cations are ~7 Å apart from each other and reorient at rates of ~10 -12 s [2][3][4][5][6]. Reorientations of the NH4 + involve protons orbiting in concert around a central stationary nitrogen atom.…”

Section: Introductionmentioning

confidence: 99%

“…Reorientations of the NH4 + involve protons orbiting in concert around a central stationary nitrogen atom. Due to the periodic nature of the potential barriers the NH4 + only exhibit two energetically favorable types of reorientations [6]: a) by 120° (C3) clockwise or anticlockwise along each of the four N-H bonds (Fig. 1b); and b) by 180° (C2) or 90° (C4) along the a, b, c axes of the lattice (Fig.…”

Section: Introductionmentioning

confidence: 99%

Electric polarization and magnetic properties of (NH4)1–xKxI (x = 0.05–0.17)

Meng

Zhao

et al. 2023

Journal of Alloys and Compounds

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Nuclear magnetic relaxation study of the establishment of order in the ammonium halides

Cited by 19 publications

References 29 publications

Magnetic Ordering of Ammonium Cations in NH₄I, NH₄Br, and NH₄Cl

Magnetic Ordering of Ammonium Cations in NH₄I, NH₄Br, and NH₄Cl

Rotational Motion of the Ammonium Ions in (NH₄)₃H(SeO₄)₂ Studied by NMR

Electric polarization and magnetic properties of (NH4)1–xKxI (x = 0.05–0.17)

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Nuclear magnetic relaxation study of the establishment of order in the ammonium halides

Cited by 19 publications

References 29 publications

Magnetic Ordering of Ammonium Cations in NH4I, NH4Br, and NH4Cl

Magnetic Ordering of Ammonium Cations in NH4I, NH4Br, and NH4Cl

Rotational Motion of the Ammonium Ions in (NH4)3H(SeO4)2 Studied by NMR

Electric polarization and magnetic properties of (NH4)1–xKxI (x = 0.05–0.17)

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Magnetic Ordering of Ammonium Cations in NH₄I, NH₄Br, and NH₄Cl

Magnetic Ordering of Ammonium Cations in NH₄I, NH₄Br, and NH₄Cl

Rotational Motion of the Ammonium Ions in (NH₄)₃H(SeO₄)₂ Studied by NMR