Magnetic properties of NH4Al(SO4)2•12H2O: Evidence of glass behavior based on proton orbitals

Lei Meng; Chu Xin Peng; Chen He; Fei Yen

doi:10.1016/j.scriptamat.2021.114184

Magnetic properties of NH₄Al(SO₄)₂•12H₂O: Evidence of glass behavior based on proton orbitals

Lei Meng
, Chu Xin Peng
, Chen He
, Fei Yen^*

^*Corresponding author for this work

Harbin Institute of Technology

Research output: Contribution to journal › Article › peer-review

4 Scopus citations

Abstract

The polarity of the magnetic susceptibility χ(T) of ammonium alum NH₄Al(SO₄)₂•12H₂O single crystals below its ferroelectric Curie temperature T_C is identified to depend only on the cooling rate. To explain this, we consider reorienting distorted NH₄⁺ to carry weak magnetic and electric dipole moments that are linearly coupled. Slow cooling allows the dipole moments to align which enhances χ(T) to become positive. However, due to energy degeneracy of rotational motion and geometric frustration of the NH₄⁺, faster cooling rates render the system to become an orientational glass state causing χ(T) to remain negative. Specific heat measurements also show the presence of excess entropy below a negative anomaly near 53 K. Our findings identify a possible new class of non-equilibrium system with potential applications in non-volatile memory devices.

Original language	English
Article number	114184
Journal	Scripta Materialia
Volume	205
DOIs	https://doi.org/10.1016/j.scriptamat.2021.114184
State	Published - Dec 2021
Externally published	Yes

Keywords

Dynamic phenomena
Magnetic structure
Non-equilibrium system
Non-volatile memory
Order-disorder phenomena

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10.1016/j.scriptamat.2021.114184

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title = "Magnetic properties of NH4Al(SO4)2•12H2O: Evidence of glass behavior based on proton orbitals",

abstract = "The polarity of the magnetic susceptibility χ(T) of ammonium alum NH4Al(SO4)2•12H2O single crystals below its ferroelectric Curie temperature TC is identified to depend only on the cooling rate. To explain this, we consider reorienting distorted NH4+ to carry weak magnetic and electric dipole moments that are linearly coupled. Slow cooling allows the dipole moments to align which enhances χ(T) to become positive. However, due to energy degeneracy of rotational motion and geometric frustration of the NH4+, faster cooling rates render the system to become an orientational glass state causing χ(T) to remain negative. Specific heat measurements also show the presence of excess entropy below a negative anomaly near 53 K. Our findings identify a possible new class of non-equilibrium system with potential applications in non-volatile memory devices.",

keywords = "Dynamic phenomena, Magnetic structure, Non-equilibrium system, Non-volatile memory, Order-disorder phenomena",

author = "Lei Meng and Peng, \{Chu Xin\} and Chen He and Fei Yen",

note = "Publisher Copyright: {\textcopyright} 2021 Acta Materialia Inc.",

year = "2021",

month = dec,

doi = "10.1016/j.scriptamat.2021.114184",

language = "英语",

volume = "205",

journal = "Scripta Materialia",

issn = "1359-6462",

publisher = "Acta Materialia Inc",

}

TY - JOUR

T1 - Magnetic properties of NH4Al(SO4)2•12H2O

T2 - Evidence of glass behavior based on proton orbitals

AU - Meng, Lei

AU - Peng, Chu Xin

AU - He, Chen

AU - Yen, Fei

PY - 2021/12

Y1 - 2021/12

N2 - The polarity of the magnetic susceptibility χ(T) of ammonium alum NH4Al(SO4)2•12H2O single crystals below its ferroelectric Curie temperature TC is identified to depend only on the cooling rate. To explain this, we consider reorienting distorted NH4+ to carry weak magnetic and electric dipole moments that are linearly coupled. Slow cooling allows the dipole moments to align which enhances χ(T) to become positive. However, due to energy degeneracy of rotational motion and geometric frustration of the NH4+, faster cooling rates render the system to become an orientational glass state causing χ(T) to remain negative. Specific heat measurements also show the presence of excess entropy below a negative anomaly near 53 K. Our findings identify a possible new class of non-equilibrium system with potential applications in non-volatile memory devices.

AB - The polarity of the magnetic susceptibility χ(T) of ammonium alum NH4Al(SO4)2•12H2O single crystals below its ferroelectric Curie temperature TC is identified to depend only on the cooling rate. To explain this, we consider reorienting distorted NH4+ to carry weak magnetic and electric dipole moments that are linearly coupled. Slow cooling allows the dipole moments to align which enhances χ(T) to become positive. However, due to energy degeneracy of rotational motion and geometric frustration of the NH4+, faster cooling rates render the system to become an orientational glass state causing χ(T) to remain negative. Specific heat measurements also show the presence of excess entropy below a negative anomaly near 53 K. Our findings identify a possible new class of non-equilibrium system with potential applications in non-volatile memory devices.

KW - Dynamic phenomena

KW - Magnetic structure

KW - Non-equilibrium system

KW - Non-volatile memory

KW - Order-disorder phenomena

UR - https://www.scopus.com/pages/publications/85113274087

U2 - 10.1016/j.scriptamat.2021.114184

DO - 10.1016/j.scriptamat.2021.114184

M3 - 文章

AN - SCOPUS:85113274087

SN - 1359-6462

VL - 205

JO - Scripta Materialia

JF - Scripta Materialia

M1 - 114184

ER -

Magnetic properties of NH₄Al(SO₄)₂•12H₂O: Evidence of glass behavior based on proton orbitals

Abstract

Keywords

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